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Naval Education and 
Training Command 



NAVEDTRA 12204 
May 1990 
0502-LP-2 13-11 00 



Training Manual 
(TRAMAN) 




Machinery 
Repairman 3 & 2 



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DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. 



Nonfederal government personnel wanting a copy of this document 
must use the purchasing instructions on the inside cover. 



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S/N0502-LP-213-1100 



The terms training manual (TRAMAN) and 
nonresident training course (NRTC) are now the 
terms used to describe Navy nonresident training 
program materials. Specifically, a TRAMAN in- 
cludes a rate training manual (RTM), officer text 
(OT), single subject training manual (SSTM), or 
modular single or multiple subject training manual 
(MODULE); and an NRTC includes nonresident 
career course (NRCC), officer correspondence 
course (OCC), enlisted correspondence course 
(ECC), or combination thereof. 



Although the words "he," "him," and "his" 
are used sparingly in this manual to enhance 
communication, they are not intended to be 
gender driven nor to affront or discriminate 
against anyone reading this text. 



DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. 



this document must write to Superintendent of Documents, 
t Commanding Officer, Naval Publications and Forms Center, 
tention: Cash Sales, for price and availability. 




MACHINERY REPAIRMAN 3 & 2 



NAVEDTRA 12204 




1990 Edition Prepared by 
MRCM Reynaldo R. Romero 




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PREFACE 



This Training Manual (TRAMAN) and Nonresident Training Course 
(NRTC) form a self-study package to teach the theoretical knowledge and 
mental skills needed by the Machinery Repairman Third Class and Machinery 
Repairman Second Class. To most effectively train Machinery Repairmen, 
this package may be combined with on-the-job training to provide the necessary 
elements of practical experience and observation of techniques demonstrated 
by more senior Machinery Repairmen. 

Completion of the NRTC provides the usual way of satisfying the 
requirements for completing the TRAMAN. The set of assignments in the 
NRTC includes learning objectives and supporting questions 
designed to help the student learn the materials in the TRAMAN. 



1990 Edition 



Stock Ordering No. 
0502-LP-213-1100 



Published by 

NAVAL EDUCATION AND TRAINING PROGRAM 
MANAGEMENT SUPPORT ACTIVITY 



UNITED STATES 

GOVERNMENT PRINTING OFFICE 
WASHINGTON, D.C.: 1990 



THE UNITED STATES NAVY 



GUARDIAN OF OUR COUNTRY 

The United States Navy is responsible for maintaining control of the 
sea and is a ready force on watch at home and overseas, capable of 
strong action to preserve the peace or of instant offensive action to 
win in war. 

It is upon the maintenance of this control that our country's glorious 
future depends; the United States Navy exists to make it so. 



WE SERVE WITH HONOR 

Tradition, valor, and victory are the Navy's heritage from the past. To 
these may be added dedication, discipline, and vigilance as the 
watchwords of the present and the future. 

At home or on distant stations we serve with pride, confident in the 
respect of our country, our shipmates, and our families. 

Our responsibilities sober us; our adversities strengthen us. 

Service to God and Country is our special privilege. We serve with 
honor. 



THE FUTURE OF THE NAVY 

The Navy will always employ new weapons, new techniques, and 
greater power to protect and defend the United States on the sea, 
under the sea, and in the air. 

Now and in the future, control of the sea gives the United States her 
greatest advantage for the maintenance of peace and for victory in 
war. 

Mobility, surprise, dispersal, and offensive power are the keynotes of 
the new Navy. The roots of the Navy lie in a strong belief in the 
future, in continued dedication to our tasks, and in reflection on our 
heritage from the past. 

Never have our opportunities and our responsibilities been greater. 



CONTENTS 



CHAPTER Page 

1. Scope of the Machinery Repairman Rating 1-1 

2. Toolrooms and Tools 2-1 

3. Layout and Benchwork 3-1 

4. Metals and Plastics 4-1 

5. Power Saws and Drilling Machines 5-1 

6. Offhand Grinding of Tools 6-1 

7. Lathes and Attachments 7-1 

8. Basic Engine Lathe Operations 8-1 

9. Advanced Engine Lathe Operations 9-1 

10. Turret Lathes and Turret Lathe Operations 10-1 

1 1 . Milling Machines and Milling Operations 11-1 

12. Shapers, Planers, and Engravers 12-1 

13. Precision Grinding Machines 13-1 

14. Metal Buildup 14-1 

15. The Repair Department and Repair Work 5-1 

APPENDIX 

I. Tabular Information of Benefit to 

Machinery Repairmen AI-1 

II. Formulas for Spur Gearing AIM 

III. Derivation Formulas for Diametral Pitch System AIII-1 

IV. Glossary AIV-1 

INDEX INDEX-1 



111 



CREDITS 



The illustrations indicated below are included in this edition of Machinery 
Repairman 3 & 2, through the courtesy of the designated companies, 
publishers, and associations. Permission to use these illustrations is gratefully 
acknowledged. Permission to reproduce these illustrations and other materials 
in this publication should be obtained from the source. 



Source 

Atlas Press Company, Clausing 
Corporation 

Brown & Sharpe Manufacturing 
Company 

Cincinnati Milacron Marketing 
Co. 

Cincinnati Inc. 
Devlieg-Sundstrand 
DoAlI Company 

Kearney & Trecker Corporation 
Lars Machine, Inc. 

Monarch Tool Company 

Rockford Line 

SIFCO Selective Plating 



South Bend Lathe Works 



Warner & Swasey Co. 



Figures 



11-3 



11-8, 11-9, 11-13, 11-14, 11-16, 11-17, 13-20 



11-1, 11-2, 11-4, 11-5, 11-12, 11-13, 11-15, 11-18, 11-19, 11-20, 
11-21, 11-83, 13-10, 13-11, 13-12, 13-15, 13-23, 13-24, 13-25 

12-1, 12-3 
10-42, 10-43 

5-3, 5-5, 5-6, 5-7, 5-8, 5-9, 5-10, 5-11, 5-12, 5-13, 5-14, 5-15, 5-16, 
5-17, 5-18, 5-19, 5-20, 5-21, 5-22, 5-23, 5-24 

11-11 

12-19, 12-20, 12-21, 12-22, 12-23, 12-24, 12-25, 12-26, 12-27, 
12-28, 12-29, 12-30, 12-31, 12-32, and table 12-2 

7-1 
12-13 

14-11, 14-12, 14-13, 14-14, 14-15, 14-16, 14-17, 14-18, 14-19, 
tables 14-3, 14-4, 14-5, 14-6, 14-7, 14-8, 14-9, 14-10, 14-11, 14-12 
and all inserts in Chapter 14 

7-2, 7-5, 7-6, 7-8, 7-9, 7-10, 7-11, 7-12, 7-13, 7-14, 7-15, 7-16, 
7-17, 7-27, 7-29, 7-32, 7-33, 7-34, 7-35, 7-36, 7-37, 7-39, 7-40, 
8-2, 8-4, 8-6, 8-9, 8-10, 8-11, 8-16, 8-18, 8-19, 8-20, 8-21, 8-22, 
8-23, 8-24, 8-25, 8-26, 8-27, 8-28, 8-29, 9-2, 9-3, 9-4, 9-5, 9-6, 
9-7, 9-8, 9-10, 9-11, 9-13, 9-19, 9-20, 9-21, 9-23, 9-24, 9-25, 9-30 

10-3, 10-4, 10-5, 10-6, 10-7, 10-8, 10-9, 10-10, 10-11, 10-12, 10-13, 
10-14, 10-15, 10-16, 10-17, 10-18, 10-19, 10-21, 10-24, 10-25, 
10-26, 10-30, 10-31, 10-34, 10-35, 10-36, 10-37, 10-38, 10-39, 
10-40, 10-41, 13-3, 13-13 



IV 



CHAPTER 1 

SCOPE OF THE 
MACHINERY REPAIRMAN RATING 



The official description of the scope of the 
Machinery Repairman rating is to "perform 
organizational and intermediate maintenance on 
assigned equipment and in support of other ships, 
requiring the skillful use of lathes, milling 
machines, boring mills, grinders, power hack- 
saws, drill presses, and other machine tools; 
portable machinery; and handtools and measuring 
instruments found in a machine shop." That is 
a very general statement, not meant to define 
completely the types of skills and supporting 
knowledge that an MR is expected to have in the 
different paygrades. The Occupational Standards 
for Machinery Repairman contain the require- 
ments that are essential for all aspiring Machinery 
Repairmen to read and use as a guide in planning 
for advancement. 

The job of restoring machinery to good work- 
ing order, ranging as it does from the fabrication 
of a simple pin or bushing to the complete 
rebuilding of an intricate gear system, requires 
skill of the highest order at each task level. Often, 
in the absence of dimensional drawings or other 
design information, a Machinery Repairman must 
depend upon ingenuity and know-how to 
successfully fabricate a repair part. 

One of the important characteristics you will 
gain from becoming a well trained and skilled 
Machinery Repairman is versatility. As you gain 
knowledge and skill in the operation of the many 
different types of machines found in Navy 
machine shops, you will realize that even though 
a particular machine is used mostly for certain 
types of jobs, it may be capable of accepting many 
others. Your imagination will probably be your 
limiting factor and if you keep your eyes, ears, 
and mind open, you will discover that there are 
many things going on around you that can 
broaden your base of knowledge. You will find 
a certain pleasure and a source of pride in develop- 
ing new and more efficient ways to do something 
that has become so routine that everyone else 
simply accepts the procedure currently being used 
as the only one that will work. 



The skill acquired by a Machinery Repairman 
in the Navy is easily translated into several skills 
found in the machine shops of private industry. 
In fact, you would be surprised at the depth and 
range of your knowledge and skill compared to 
your civilian counterpart, based on a somewhat 
equal length of experience. The machinist trade 
in private industry tends to break job descriptions 
into many different titles and skill levels. The 
beginning skill level and one in which you will 
surely become qualified is "Machine Tool 
Operator," a job often done by semiskilled 
workers. The primary requirement of the job is 
to observe the operation, disengage the machine 
in case of problems and possibly maintain manual 
control over certain functions. Workers who do 
these jobs usually have the ability to operate a 
limited number of different types of machines. 
Another job description found in private industry 
is "Layout Man." The requirement of this job 
is to layout work that is to be machined by some- 
one else. An understanding of the operation and 
capabilities of the different machines is required, 
as well as the ability to read blueprints. As you 
progress in your training in the Machinery 
Repairman rating you will become proficient in 
interpreting blueprints and in planning the 
required machining operations. You will find that 
laying out intricate parts is not so difficult with 
this knowledge. A third job description is "Set- 
up Man," a job which requires considerable 
knowledge and skill, all within what you can 
expect to gain as a Machinery Repairman. A set- 
up man is responsible for placing each machine 
accessory and cutting tool in the exact position 
required to permit accurate production of work 
by a machine tool operator. An "All Around 
Machinist" in private industry is the job for which 
the average Machinery Repairman would qualify 
as far as knowledge and skill are concerned. 
This person is able to operate all machines in the 
shop and manufacture parts from blueprints. 
Some Machinery Repairmen will advance their 
knowledge and skills throughout their Navy career 



1-1 



to the point that they could move into a job as 
a "Tool and Die Maker" with little trouble. They 
also acquire a thorough knowledge of engineer- 
ing data related to design limitations, shop math 
and metallurgy. There are many other related 
fields in which an experienced Machinery Repair- 
man could perform instrument maker, research 
and development machinist, toolroom operator, 
quality assurance inspector, and of course the 
supervisory jobs such as foreman or 
superintendent. 

The obvious key to holding down a position 
of higher skill, responsibility, and pay is the same 
both in the Navy and in private industry. You 
must work hard, take advantage of the skills and 
knowledge of those around you, and take pride 
in what you do regardless of how unimportant 
it may seem to you. You have a great opportunity 
ahead of you as a Machinery Repairman in the 
Navy; a chance to make your future more secure 
than it might have been. 



TYPICAL ASSIGNMENT 
AND DUTIES 

As a Machinery Repairman you can be 
assigned to a tour of duty aboard almost any type 
of surface ship, from a small fleet tug, which has 
a small 10- or 12-inch lathe, a drill press and a 
grinder, to a large aircraft carrier that is almost 
as well equipped in the machine shop as a tender 
or repair ship. You will find that although a 
ship's workspace is relatively small the machine 
shop will have more equipment than you might 
imagine. A lathe, drill press and grinder can 
almost be assured, but in many cases a milling 
machine and a second lathe are also available. A 
tender or repair ship is similar to a factory in the 
types of equipment that are installed. You will 
find the capabilities of such a ship to be very 
extensive in all areas required to maintain the 
complex ships of today's Navy. A Machinery 
Repairman is not destined to spend an entire 
career on sea duty. There are many shore 
establishments where you may be assigned. The 
Navy has shore-based repair activities located at 
various places throughout the United States and 
overseas. Most of these have wide-ranging 
capabilities for performing the required 
maintenance. There are general billets or 
assignments ashore that will not necessarily be 
associated with the Machinery Repairman rating, 
but which add to an individual's overall experience 
in other ways. 



It would be difficult to detail the duties that 
you may perform at each of your assignments. 
You will find that on small ships you may be the 
only Machinery Repairman aboard. This requires 
that you be self-motivated toward learning all you 
can to increase your ability as a Machinery Repair- 
man and that you seek advice from sources off 
of your ship when you have an opportunity. You 
will be surprised at how good you really are when 
you make an honest effort to do your best. 
Regardless of your assignment, you will have an 
opportunity to work with personnel from other 
ratings. This can be an experience in itself. There 
are many interesting skills to be found in the 
Navy. None of them are easy, but many will offer 
you some amount of knowledge that will increase 
your effectiveness as a Machinery Repairman. 



TRAINING 

Training is the method by which everyone 
becomes knowledgeable of and skilled in any 
activity, whether it's a job, a sport or something 
as routine as eating the proper foods. Training 
can take many forms and can be a conscientious 
or unconscientious effort on your part. However, 
you will make the most progress when you 
recognize the need to increase your level of 
knowledge, take the required action to obtain the 
training and fully apply all your efforts and 
resources to realize the maximum benefit from the 
training. In the following paragraphs, we will 
present a brief description of each type of train- 
ing available to a Machinery Repairman. Keep in 
mind that the information listed is peculiar to your 
rating and that the Navy has many other programs 
available which will allow you to increase your 
general education. You can obtain information 
concerning these programs from your career 
counselor or education officer. 

FORMAL SCHOOLS 

The Navy has available several schools which 
provide an excellent background in the Machinery 
Repairman rating. You may have an opportunity 
to attend one or more of them during your career 
in the Navy. 

The fundamentals of machine shop practice 
are taught in Machinery Repairman "A" school. 
Classroom instruction provides the theory of basic 
operating procedures, safety precautions and 
certain project procedures, while time spent in the 
shop provides hands-on experience, supervised by 



1-2 



a trained and skilled instructor. Some of the 
equipment that you can expect to work with in 
this course are lathes, milling machines, drill 
presses, band saws, cutoff saws, pedestal grinders 
and engraving machines. The length and specific 
content of the course may vary from time to time 
to accommodate the needs of the fleet. You will 
have no difficulty in performing the work in a 
Navy machine shop if you apply yourself in MR 
"A" school. 

Advanced machine shop practice and the heat 
treatment of metals are taught in Navy schools 
also. These courses are usually attended by 
personnel in their second and subsequent 
enlistments at "C" school. Course content 
generally covers the information and associated 
equipment required for advancement to MR1 and 
MRC, although the schools are not required to 
establish eligibility for advancement. 

You should consult with your leading petty 
officer or career counselor to obtain the most 
current information regarding school availability 
and your eligibility to request attendance. 



TRAINING MANUALS 
AND NONRESIDENT 
TRAINING COURSES 

Navy training manuals and nonresident train- 
ing courses are designed as a self-study method 
to provide instruction to personnel in a variety 
of subjects. You can choose your own pace in 
working the courses, and you are allowed to refer 
to the book when trying to decide on the best or 
correct answer. If you are to learn anything, you 
must work the course yourself and not take the 
answers from someone else. Some training 
manuals and nonresident training courses are 
mandatory for you to complete to meet advance- 
ment requirements. These courses are listed in the 
Manual for Advancement, BUPERINST 1430.16 
(series), and in the current (revised annually) issue 
of the Bibliography for Advancement Study, 
NAVEDTRA 10052 (series), where they are 
indicated by asterisks (*). Remember that as you 
advance you are responsible for the information 
in the training manuals for the paygrades below 
yours, in addition to the courses for the next 
higher paygrade. A course offers an excellent 
opportunity to become familiar with a subject 
when you cannot be personally involved with the 
equipment. There are many small but important 
points that will be covered in a course that you 
otherwise may not learn. 



ON-THE-JOB TRAINING 

On-the-job training is probably the most 
valuable of all the training methods available to 
you. This is where you put the textbook theories 
and general procedures into specific job practice 
in personal contact with the problem at hand. All 
those unfamiliar terms that you read about in a 
course now begin to fit into a plan that makes 
sense to you. The one very important thing for 
you to remember is that when you are unsure 
about something, ask questions. An unusual job 
experience is of little value to you if you have to 
wing your way through it tooth and nail, guess- 
ing at each new step. The people that you work 
with and for had to learn what they know by 
asking questions, so they won't think you any less 
efficient or valuable when you ask. There will be 
opportunities to tackle jobs which are difficult and 
seldom done, jobs which offer a great deal of 
experience and knowledge. These are the jobs that 
you should be really aggressive in pursuing and 
eager to accept. Regardless of the profession or 
the employer, the person who gets ahead is usually 
the one who is highly motivated toward increasing 
personal capacity, thereby, becoming more 
valuable to his or her employer. The Navy is no 
different than any other employer in this sense. 



OTHER TRAINING MANUALS 

Some of the publications you will use are 
subject to revision from time to time some at 
regular intervals, others as the need arises. When 
using any publication that is subject to revision, 
be sure that you have the latest edition. When 
using any publication that is kept current by 
means of changes, be sure you have a copy in 
which all official changes have been made. 
Studying canceled or obsolete information will not 
help you do your work or advance; it is likely to 
be a waste of time, and may even be seriously 
misleading. 

The training manuals you must use in conjunc- 
tion with this one to attain your required 
professional qualifications are: 

1. Mathematics, Vol 1, NAVEDTRA 10069 
and Mathematics, Vol. 2, NAVEDTRA 10071. 
These two volumes provide a review of the 
mathematics you will need in shop work. 

2. Blueprint Reading and Sketching, 
NAVEDTRA 10077, provides information on 
blueprint reading and layout work. 



1-3 



3. Tools and Their Uses, NAVEDTRA 10085, 
provides specific and practical information in the 
use of almost any handtool you are likely to use. 

It is important that you keep abreast of 
required training manuals. To ensure that the 
most current manual is available, you should 
check the Bibliography for Advancement Study, 
NAVEDTRA 10052 (series), and List of Train- 
ing Manuals and Correspondence Courses, 
NAVEDTRA 10061 (series). Both of these 
references are revised annually, so be sure you 
have the latest one. 

In addition, there are three sources of technical 
information that are ordinarily available on board 
your ship: (1) NAVSHIPS' Technical Manual, 
which contains the official word on all shipboard 
machinery, (2) technical manuals provided by the 
manufacturers of machinery and equipment used 
by the Navy, and (3) machinist's handbooks. Most 
of these books should be readily available. 
However, if they are not, your leading petty 
officer or division officer can request them 
through proper channels. 



SAFETY 

As a Machinery Repairman, you will be 
exposed to many different health and safety 
hazards every day. A great many of these are 
common to all personnel who work and live 
aboard a Navy ship or station, and some are 
peculiar only to personnel who are involved with 
jobs within machinery spaces. Information 
concerning these can be found in both the Fireman 
and Basic Military Requirements training manuals 
as well as instructions prepared by your 
command. In this section we shall look at some 
of the more common safety hazards you will find 
in a machine shop and some of the precautions 
you can take to prevent an injury to either yourself 
or someone else. You will find that safety is 
stressed throughout this manual as well as the 
importance of an individual's responsibility to not 
only be familiar with and observe all safe working 
standards personally, but also to encourage others 
to do so. Safety is a subject where the "learn by 
doing" method does not provide the greatest 
advantage. 

Your eyes are one of your most priceless 
possessions. When you think about this and try 
to imagine how you would get along without 
them, you will agree that the slight inconvenience 
caused by wearing safety glasses, goggles or a face 



shield is a small price to pay for eye protection. 
Wear safety glasses or goggles any time you are 
around machinery in operation, including hand- 
tools, whether powered or nonpowered. Safety 
glasses that have side guards are the most 
effective for keeping out small metal chips or 
particles from grinding wheels. You should wear 
a face shield and safety glasses at all times 
whenever you are around any grinding operation. 

Another item of protection is safety-toe shoes. 
Granted, the additional weight of the steel 
reinforced toe does not make them the most 
comfortable shoes you can wear, but they do offer 
outstanding foot protection and are much more 
comfortable than a cast. Look around your shop 
at the dents left in the deck from objects being 
dropped. Do you think your unprotected foot 
would fare any better? 

Some of the objects you will be handling in 
the shop will have sharp or ragged edges on them 
that can cut easily. You should remove as many 
of these "burrs" as possible with a file. In spite 
of your filing efforts, heavy objects will still cut 
easily where there is a corner. A pair of leather 
or heavy cotton work gloves will protect your 
hands in these cases. You should NOT wear gloves 
when operating machinery. The chances of their 
being caught are too great. 

Loose fitting clothing worn around moving 
machinery will test your strength if it is caught 
in the rotating equipment. You would be amazed 
at the strength a shirt has when being wound up 
on a machine. Rings, bracelets and other jewelry 
can snag on projections of a rotating part and take 
a finger or other part of your body off before you 
know you have a problem. 

How many times have you seen someone bend 
over and pick up a heavy object by using his or 
her back? Chances are this same person will 
eventually injure himself or herself. The correct 
way to lift any heavy object is to get as close to 
the object as you can, spread your feet about a 
foot apart and squat down by bending your knees. 
Keep your back straight during the lift. When you 
grasp the object, lift by using the muscles in your 
legs and hold the object close to your body. Walk 
slowly to your destination and lower the part 
exactly as you lifted it. If you have to lift 
something higher than your waist, seek assistance. 
Of course, there is a limit to how much weight 
anyone can safely pick up and this should not be 
exceeded. 

Good housekeeping practices may demand a 
little more of your time than you are willing to 
give on some occasions, but this is just as 



1-4 



important to a safe shop as any other measure 
you can take. Small chips made during a 
machining operation can become very slippery 
when allowed to collect on a steel deck. Long, un- 
broken chips can trip or cut someone walking past 
them. Lubricating oil that has seeped from a 
machine or a cutting oil thrown out by the 
machine can be an extreme hazard on a steel deck. 
All liquid spillage should be cleaned up right 
away. If your job is causing a hazard to other 
personnel by throwing chips or coolant into a 
passageway, speak with your supervisor about 
isolating the immediate area by stretching tape 
across the area. Unused metal stock, small and 
large parts of equipment being worked on, 
toolboxes and countless other objects should not 
be left laying around the shop where traffic can 
be expected to go or where a machine operator 
may have to be positioned. Most well organized 
shops have a place for storing all movable objects 
and this is the place for them. It will save you time 
when daily cleanup or field day comes along, and 
it may prevent a serious injury. 

To protect yourself from injury while 
operating ship machinery, there are several things 
you can do. The first thing is to make sure that 
you know how the machine operates, what each 
control lever does, the capability of the machine 
and especially where the stop button or clutch 
lever is in case an emergency stop is required. All 
guards that cover gears, drive belts, pulleys or 
deflect chips should be in place at all times. Use 
the correct tool for the job you are doing. This 
means more than using a scraper to remove paint 
instead of a 6-inch ruler. Every machine or hand- 
tool has a safe working limit that was determined 
by considering the stresses it is subjected to 
during its intended use. Excessive pressures could 
cause machine or tool failure followed by injury. 

Whenever you are operating a machine, give 
it your total concentration. Save daydreaming for 
a more relaxed time. If you must talk with some- 
one, shut your machine off. 

Electrical safety is not the private respon- 
sibility of the electricians. They can keep the 
equipment operating safely if they are notified 
when a problem exists. They cannot make 
everyone observe safety precautions when work- 
ing around electrically powered equipment. This 
is a responsibility that each individual must accept 
and carry out. 

The electrical systems used onboard ships are 
not like those found in your home, so however 
efficient you may feel you are as a handyman, 
do not attempt to make any repairs or adjustments 



on any faulty equipment on board ship. Notify 
the electric shop and let the job be done by the 
trained electricians. 

There are some basic safety precautions you 
can observe while using electrical equipment: 

Use only authorized portable electric 
equipment which has been tested by the electric 
shop within the prescribed time period and which 
is properly tagged to indicate such a test. 

Report all jury-rigged portable electrical 
equipment to the electric shop. 

When a plastic-cased or double-insulated 
electrically powered tool is available, use it in 
preference to an older metal-cased tool. 

Ensure that all metal-cased electrically 
powered tools have a three-conductor cable, a 
three-prong grounded plug and that they are 
plugged into the proper type receptacle. 

Wear rubber gloves when setting up and 
using the metal-cased tools or when working 
under particularly hazardous conditions and in 
environments such as wet decks. 

Notify the electric shop when you feel even 
a slight tingle while operating electrical equipment. 

Follow the safety precautions exactly as 
prescribed by your maintenance requirement cards 
when you perform maintenance on your 
equipment. 

Always remember that electricity strikes 
without warning and, unfortunately, we cannot 
always sit around and discuss what went wrong 
after an accident has happened. It is to your 
advantage to ask when you are not sure of 
something. NEVER take unnecessary chances by 
hurrying or being inattentive. ALWAYS THINK 
about what your are going to do before you do it. 



PURPOSES, BENEFITS, 
AND LIMITATIONS 
OF THE PLANNED 

MAINTENANCE SYSTEM 

You will soon find, if you have not done so 
already, that the continued operation of 
machinery depends on systematic and dedicated 
maintenance. The following paragraphs contain 



1-5 



a brief discussion on the purposes, benefits, and 
limitations of the Navy's formal maintenance 
system, the Planned Maintenance System. You 
will be involved in the Planned Maintenance 
System, to some degree, throughout your career 
in the Navy. 



PURPOSES 

The Planned Maintenance System (PMS) was 
established for several purposes: 

1. To reduce complex maintenance to 
simplified procedures that are easily identified and 
managed at all levels. 

2. To define the minimum planned mainte- 
nance required to schedule and control PMS 
performance. 

3. To describe the methods and tools to be 
used. 

4. To provide for the detection and prevention 
of impending casualties. 

5. To forecast and plan manpower and- 
material requirements. 

6. To plan and schedule maintenance tasks. 

7. To estimate and evaluate material readi- 
ness. 

8. To detect areas that require additional or 
improved personnel training and/or improved 
maintenance techniques or attention. 

9. To provide increased readiness of the ship. 



BENEFITS 

PMS is a tool of command. By using PMS, 
the commanding officer can readily determine 
whether his ship is being properly maintained. 
Reliability is intensified. Preventive maintenance 
reduces the need for major corrective 
maintenance, increases economy, and saves the 
cost of repairs. 

PMS assures better records, containing more 
data that can be useful to the shipboard 
maintenance manager. The flexibility of the 
system allows for programming of inevitable 
changes in employment schedules, thereby help- 
ing to better plan preventive maintenance. 

Better leadership and management can be 
realized by reducing frustrating breakdowns and 
irregular hours of work. PMS offers a means 
of improving morale and thus enhances the 
effectiveness of both enlisted personnel and 
officers. 



LIMITATIONS 

The Planned Maintenance System is not self- 
starting; it will not automatically produce good 
results. Considerable professional guidance is 
required. Continuous direction at each echelon 
must be maintained, and one individual must be 
assigned both the authority and the responsibility 
at each level of the system's operation. 

Training in the maintenance steps as well as 
in the system will be necessary. No system is a 
substitute for the actual technical ability required 
of the officers and enlisted personnel who direct 
and perform the upkeep of the equipment. 



SOURCES OF INFORMATION 

One of the most useful things you can learn 
about a subject is how to find out more about it. 
No single jmblication can give you all the 
information yougieed to perform the duties of 
your rating. You should learn where to look for 
accurate, authoritative, up-to-date information on 
all subjects related to the naval requirements for 
advancement and the occupational standards of 
your rating. 

NAVSEA PUBLICATIONS 

The publications issued by the Naval Sea 
Systems Command are of particular importance 
to engineering department personnel. Although 
you do not need to know everything in these 
publications, you should have a general idea of 
where to find the information they contain. 

Naval Ships' Technical Manual 

The Naval Ships' Technical Manual is the 
basic engineering doctrine publication of the 
Naval Sea Systems Command. The manual is kept 
up-to-date by means of quarterly changes. 

NAVSEA Deckplate 

The NAVSEA Deckplate is a bimonthly 
technical periodical published by the Naval 
Sea Systems Command for the information of 
personnel in the naval establishment on the 
design, construction, conversion, operation, 
maintenance, and repair of naval vessels and their 
equipment, and on other technical equipment and 
on programs under NAVSEA's control. This 
magazine is particularly useful because it presents 



1-6 



information that supplements and clarifies 
information contained in the Naval Ships' 
Technical Manual. It is also of considerable 
interest because it presents information on new 
developments in naval engineering. The NAVSEA 
Deckplate was formerly known as the NAVSEA 
Journal. 

MANUFACTURER'S TECHNICAL 

MANUALS 

The manufacturers' technical manuals fur- 
nished with most machinery units and many items 
of equipment are valuable sources of information 
on construction, operation, maintenance, and 
repair. The manufacturers' technical manuals that 
are furnished with most shipboard engineering 
equipment are given NAVSHIPS numbers. 

DRAWINGS 

Some of your work as a Machinery Repair- 
man requires an ability to read and work from 
mechanical drawings. You will find information 
on how to read and interpret drawings in 
Blueprint Reading and Sketching, NAVEDTRA 
10077 (series). 

In addition to knowing how to read drawings, 
you must know how to locate applicable draw- 
ings. For some purposes, the drawings included 
in the manufacturers' technical manuals for 
the machinery or equipment may give you the 
information you need. In many cases, however, 
you will need to consult the on-board drawings. 
The on-board drawings, which are sometimes 
referred to as ship's plans or ship's blueprints, are 
listed in an index called the ship drawing index 
(SDI). 

The SDI lists all working drawings that 
have a NAVSHIPS drawing number, all 
manufacturers' drawings designated as certifica- 
tion data sheets, equipment drawing lists, and 
assembly drawings that list detail drawings. The 
on-board drawings are identified in the SDI by 
an asterisk (*). 



Drawings are listed in numerical order in the 
SDI. On-board drawings are filed according to 
numerical sequence. A cross-reference list of 
S-group numbers and consolidated index numbers 
is given in Ship Work Breakdown Structure. 



ENGINEERING HANDBOOKS 

For certain types of information, you may 
need to consult various kinds of engineering 
handbooks mechanical engineering handbooks, 
marine engineering handbooks, piping hand- 
books, machinery handbooks, and other hand- 
books that provide detailed, specialized technical 
data. Most engineering handbooks contain a great 
deal of technical information, much of it arranged 
in charts or tables. To make the best use of 
engineering handbooks, use the table of contents 
and the index to locate the information you need. 



ADDENDUM 

In addition to a comprehensive index that is 
printed in the back of this manual, you will find 
the following: 

1. Appendix I contains 23 tables, such as 
decimal equivalents of fractions; division of the 
circumference of a circle; formulas for length, 
area, and volume; tapers, and so forth. You will 
find this information helpful in your everyday 
shop work. 

2. Appendix II contains formulas for spur 
gearing. 

3. Appendix III shows the derivation of 
formulas for the diametral pitch system. 

4. Appendix IV is a glossary of terms peculiar 
to the Machinery Repairman rating. 



1-7 



CHAPTER 2 

\ 

TOOLROOMS AND TOOLS 



Your proficiency as a Machinery Repairman 
is greatly influenced by your knowledge of tools 
and your skills in using them. The information 
you will need to become familiar with the correct 
use and care of the many powered and non- 
powered handtools, measuring instruments, and 
gauges is available from various sources to which 
you will have access. 

This training manual will provide information 
which applies to the tools and instruments used 
primarily by a Machinery Repairman. You can 
find additional information on tools that are 
commonly used by the many different naval 
ratings in Tools and Their Uses, NAVEDTRA 
10085. 



TOOL ISSUE ROOM 

One of your responsibilities as a Machinery 
Repairman is the operation of the tool crib or tool 
issuing room. You should ensure that the 
necessary tools are available and in good condition 
and that an adequate supply of consumable items 
(oil, wiping rags, bolts, nuts, and screws) is 
available. 

Operating and maintaining a toolroom is 
simple if the correct procedures and methods are 
used to set up the system. Some of the basic 
considerations in operating a toolroom are (1) the 
issue and custody of tools; (2) replacement of 
broken, worn, or lost tools; and (3) proper storage 
and maintenance of tools. 

ORGANIZATION OF THE TOOLROOM 

Shipboard toolrooms are limited in size by the 
design characteristics of the ship. Therefore, the 
space set aside for this purpose must be used as 
efficiently as possible. Since the number of 
tools required aboard ship is extensive, tool- 
rooms usually tend to be overcrowded. Certain 
peculiarities in shipboard toolrooms also require 
consideration. For example: The motion of the 



ship at sea requires that tools be made secure to 
prevent movement. The moisture content of the 
air requires that the tools be protected from 
corrosion. 

Permanent bins, shelves, and drawers cannot 
easily be changed in the toolroom. However, 
existing storage spaces can be reorganized by 
dividing larger bins and relocating tools to 
provide better use of space. 

Hammers, wrenches, and other tools that do 
not have cutting edges may normally be stored 
in bins. They also may be segregated by size or 
other designation. Tools with cutting edges require 
more space to prevent damage to the cutting 
edges. Usually these tools are stored on shelves 
lined with wood, on pegboards, or on hanging 
racks. Pegboards are especially adaptable for tools 
such as milling cutters. Some provision must be 
made to keep these tools from falling off of the 
boards when the ship is rolling. Precision tools 
(micrometers, dial indicators and so forth) should 
be stored in felt-lined wooden boxes in a cabinet 
to reduce the effects of vibration. This arrange- 
ment allows a quick daily inventory. It also 
prevents the instruments from being damaged by 
contact with other tools. Rotating bins can be used 
to store large supplies of small parts, such as nuts 
and bolts. Rotating bins provide rapid selection 
from a wide range of sizes. Figures 2-1, 2-2, and 
2-3 show some of the common methods of tool 
storage. 

Frequently used tools should be located near 
the issuing door so that they are readily available. 
Seldom used tools should be placed in out of the 
way areas such as on top of bins or in spaces that 
cannot be used efficiently because of size and 
shape. Heavy tools should be placed in spaces or 
areas where a minimum of lifting is required. 
Portable power tools should be stored in racks. 
Provisions should be made for storage of electrical 
extension cords and the cords of electric power 
tools. 

All storage areas such as bins, drawers, and 
lockers should be clearly marked for ease in 



2-1 




Figure 2-1. Method of tool storage. 



28.333.1 




Figure 2-2. Method of tool storage. 



28.334 



2-2 




28.335 



Figure 2-3. Method of tool storage. 



2-3 



You will be responsible for the condition of 
all the tools and equipment in the toolroom. You 
should inspect all tools as they are returned to 
determine if they need repairs or adjustment. Set 
aside a space for damaged tools to prevent issue 
of these tools until they have been repaired. 

You should wipe clean all returned tools and 
give their metal surfaces a light coat of oil. Check 
all precision tools upon issue and return to 
determine if they are accurate. Keep all spaces 
clean and free of dust to prevent foreign matter 
from getting into the working parts of tools. 

Plan to spend a portion of each day recondi- 
tioning damaged tools. This is important in keep- 
ing the tools available for issue and will prevent 
an accumulation of damaged tools. 

CONTROL OF TOOLS 

You will issue and receive tools and maintain 
custody of the tools. Be sure that a method of 
identifying a borrower with the tool is established, 
and that provisions are made for periodic 
inventory of available tools. 

There are two common methods of tool 
issue control: the tool check system and the 
mimeographed form or tool chit system. Some 
toolrooms may use a combination of both of these 
systems. For example: Tool checks may be used 
for machine shop personnel, and mimeographed 
forms may be used for personnel outside the shop. 

Tool checks are either metal or plastic disks 
stamped with numbers that identify the borrower. 
In this system the borrower presents a check for 
each tool, and the disk is placed on a peg near 
the space from which the tool was taken. The 
advantage of this system is that very little time 
is spent completing the process. 

If the tools are loaned to all departments in 
the ship, mimeographed forms generally are used. 
The form has a space for listing the tools, the 
borrower's name, the division or department, and 
the date. This system has the advantage of 
allowing anyone in the ship's crew to borrow tools 
and of keeping the toolroom keeper informed as 
to who has the tools, and how long they have been 
out. 

You must know the location of tools and 
equipment out on loan, how long tools have 
been out, and the amount of equipment and 
consumable supplies you have on hand. To know 
this, you will have to make periodic inventories. 



help you decide whether more strict control of 
equipment is required and whether you need to 
procure more tools and equipment for use. 

Some selected items, called controlled 
equipage, will require an increased level of 
management and control due to their high cost, 
vulnerability to pilferage, or their importance to 
the ship's mission. The number of tools and 
instruments in this category under the control of 
a Machinery Repairman is generally small. 
However, it is important that you be aware of 
controlled equipage items. You can get detailed 
information about the designation of controlled 
equipage from the supply department of your 
activity. When these tools are received from the 
supply department, your department head will be 
required to sign a custody card for each item, 
indicating a definite responsibility for manage- 
ment of the item. The department head will then 
require signed custody cards from personnel 
assigned to the division or shop where the item 
will be stored and used. As a toolroom keeper, 
you may be responsible for controlling the issue 
of these tools and ensuring their good condition. 
If these special tools are lost or broken beyond 
repair, replacement cannot be made until the 
correct survey procedures have been completed. 
Formal inventories of these items are conducted 
periodically as directed by your division officer 
or department head. 

As a toolroom keeper, you may have 
additional duties as a supply representative for 
your department or division. You can find 
information on procurement of tools and supplies 
in Military Requirements for Petty Officer 3 & 
2, NAVEDTRA 10056. 

SAFETY IN THE TOOLROOM 
AND THE SHOP 

The toolroom, because of its relatively small 
size and the large quantity of different tools which 
are stored in it, can become very dangerous if all 
items are not kept stored in their proper places. 
At sea the toolroom can be especially hazardous 
if the proper precautions are not followed for 
securing all drawers, bins, pegboards, and other 
storage facilities. Fire hazards are sometimes 
overlooked in the toolroom. When you consider 
the flammable liquids and wiping rags stored in 
or issued from the toolroom, there is a real danger 
present. 



2-4 



Several of your jobs are directly connected to the 
good working order and safe use of tools in the 
shop. If you were to issue an improperly ground 
twist drill to someone who did not have the 
experience to recognize the defect, the chances of 
the person being injured by the drill "digging in" 
or throwing the workpiece out of the drill press 
would be very real. A wrench which has been 
sprung or worn oversize can become a real 
"knucklebuster" to any unsuspecting user. An 
outside micrometer out of calibration can cause 
trouble if someone is trying to press fit two parts 
together using a hydraulic press. An electric- 
powered handtool that was properly inspected and 
tagged last week but has had the plug crushed 
since then can kill the user. The list of potential 
disasters that you as an individual have some 
influence in preventing is endless. The important 
thing to remember is that you as a toolroom 
keeper contribute more to the mission of the Navy 
than first meets the eye. 



SHOP MEASURING GAUGES 

Practically all shop jobs require measuring or 
gauging. You will most likely measure or gauge 
flat or round stock; the outside diameters of rods, 
shafts, or bolts; slots, grooves, and other 
openings; thread pitch and angle; spaces between 
surfaces; or angles and circles. 

For some of these operations, you will have 
a choice of which instrument to use, but in other 
instances you will need a specific instrument. For 
example, when precision is not important, a 
simple rule or tape will be suitable, but in other 
instances, when precision is of prime importance, 
you will need a micrometer to obtain measure- 
ment of desired accuracy. 

The term "gauge," as used in this chapter 
identifies any device which can be used to 
determine the size or shape of an object. There 
is no significant difference between gauges and 
measuring instruments. They are both used to 
compare the size or shape of an object against a 
scale or fixed dimension. However, there is a 
distinction between measuring and gauging which 
is easily explained by an example. Suppose that 
you are turning work in a lathe and want to know 
the diameter of the work. Take a micrometer, or 
perhaps an outside caliper, adjust its opening 
to the exact diameter of the workpiece, and 



time to measure it, set the caliper at a reading 
slightly greater than the final dimension desired; 
then, at intervals during turning operations, 
gauge, or "size," the workpiece with the locked 
instrument. After you have reduced the workpiece 
dimension to the dimension set on the instrument, 
you will, of course, need to measure the work 
while finishing it to the exact dimension desired. 

ADJUSTABLE GAUGES 

You can adjust adjustable gauges by moving 
the scale or by moving the gauging surface to the 
dimensions of the object being measured or 
gauged. For example, on the dial indicator, you 
can adjust the face to align the indicating hand 
with the zero point on the dial. On verniers, 
however, you move the measuring surface to the 
dimensions of the object being measured. 

Dial Indicators 

Dial indicators are used by Machinery Repair- 
man in setting up work in machines and in 
checking the alignment of machinery. Proficiency 
in the use of the dial indicator will require a lot 
of practice, and you should use the indicator as 
often as possible to aid you in doing more accurate 
work. 

Dial indicator sets (fig. 2-4) usually have 
several components that permit a wide variation 



CLAMP AND 
CLAMP HOLDING 
INDICATOR R D ' 

HOLDING ROD 



HOLE 
ATTACHMENT 




TOOL 
POST- 
HOLDER 



Figure 2-4. Universal dial indicator. 



2-5 



nexiDiiity or setup, tne clamp and noiamg roas 
permit setting the indicator to the work, the hole 
attachment indicates variation or run out of 
inside surfaces of holes, and the tool post holder 



When you are preparing to use a dial 
indicator, there are several things that you should 
check. Dial indicators come in different degrees 
of accuracy. Some will give readings to one 




Figure 2-5 Applications of a dial indicator. 



2-6 



(0.005) of an inch. Dial indicators also differ 
in the total range or amount that they will 
indicate. If a dial indicator has a total of one 
hundred thousandths of an (0.100) inch in 
graduations on its face and has a total range 
of two hundred thousandths (0.200) of an 
inch, the needle will only make two revolutions 
before it begins to exceed its limit and jams 
up. The degree of accuracy and range of a dial 
indicator is usually shown on its face. Before you 
use a dial indicator, carefully depress the contact 
point and release it slowly; rotate the movable dial 
face so the dial needle is on zero. Depress and 
release the contact point again and check to 
ensure that the dial pointer returns to zero; if it 
does not, have the dial indicator checked for 
accuracy. 



A vernier caliper (fig. 2-6) can be used to 
measure both inside and outside dimensions. 
Position the appropriate sides of the jaws on the 
surface to be measured and read the caliper from 
the side marked inside or outside as required. 
There is a difference in the zero marks on the two 
sides that is equal to the thickness of the tips of 
the two jaws, so be sure to read the correct side. 
Vernier calipers are available in sizes ranging from 
6 inches to 6 feet and are graduated in increments 
of thousandths (0.001) of an inch. The scales on 
vernier calipers made by different manufacturers 
may vary slightly in length or number of divisions; 
however, they are all read basically the same way. 
Simplified instructions for interpreting the 
readings are covered in Tools and Their Uses, 
NAVEDTRA 10085. 




28.314 



Figure 2-6. Vernier caliper. 



2-7 



out work for machining operations or to check 
the dimensions on surfaces which have been 
machined. Attachments for the gauge include the 
offset scriber shown attached to the gauge in 
figure 2-7. The offset scriber lets you measure 
from the surface plate with readings taken directly 
from the scale without having to make any 
calculations. As you can see in figure 2-7, if you 
were using a straight scriber, you would have to 
calculate the actual height by taking into account 
the distance between the surface plate and the zero 
mark. Some models have a slot in the base for 
the scriber to move down to the surface and a scale 
that permits direct reading. Another attachment 
is a rod that permits depth readings. Small dial 



as a vernier caliper. 



Dial Vernier Caliper 

A dial vernier caliper (fig. 2-8) looks much like 
a standard vernier caliper and is also graduated 
in one-thousandths (0.001) of an inch. The main 
difference is that instead of a double scale, as on 
the vernier caliper, the dial vernier has the 
inches marked only along the main body of the 
caliper and a dial with two hands to indicate 
hundredths (0.100) and thousandths (0.001) of an 
inch. The range of the dial vernier caliper is 
usually 6 inches. 




28.4(28D) 



Figure 2-7. Vernier height gauge. 



2-8 




A, MEASURING THE INSIDE 




B. MEASURING THE OUTSIDE 



28.315 



Figure 2-8. Dial vernier caliper. 



2-9 




28.316 



Figure 2-9. Dial bore gauge. 



\jlic ui LUC iiiusi aiA.uj.aLe luuia iui 

a cylindrical bore or for checking a bore for out- 
of-roundness or taper is the dial bore gauge. The 
dial bore gauge (fig. 2-9) does not give a 
direct measurement; it gives you the amount of 
deviation from a preset size or the amount of 
deviation from one part of the bore to another. 
A master ring gauge, outside micrometer, or 
vernier caliper can be used to preset the gauge. 
A dial bore gauge has two stationary spring- 
loaded points and an adjustable point to permit 
a variation in range. These three points are evenly 
spaced to allow accurate centering of the tool in 
the bore. A fourth point, the tip of the dial 
indicator, is located between the two stationary 
points. By simply rocking the tool in the bore, 
you can observe the amount of variation on the 
dial. Accuracy to one ten-thousandth (0.0001) of 
an inch is possible with some models of the dial 
bore gauge. 

Internal Groove Gauge 

The internal groove gauge is very useful for 
measuring the depth of an O-ring groove or other 
recesses inside a bore. This tool lets you measure 
a deeper recess and one located farther back in 
the bore than if you were to use an inside caliper. 
As with the dial bore gauge, this tool must be set 
with gauge blocks, a vernier caliper, or an out- 
side micrometer. The reading taken from the dial 
indicator on the groove gauge represents the dif- 
ference between the desired recess or groove depth 
and the measured depth. 

Universal Vernier Bevel Protractor 

The universal vernier bevel protractor (fig. 
2-10) is the tool you will use to lay out or measure 
angles on work to very close tolerances. The 
vernier scale on the tool permits measuring an 
angle to within 1/12 (5 minutes) and can be used 
completely through 360. Interpreting the reading 
on the protractor is similar to the method used 
on the vernier caliper. 

Universal Bevel 

The universal bevel (fig. 2-11), because of the 
offset in the blade, is very useful for bevel gear 
work and for checking angles on lathe workpieces 
which cannot be reached with an ordinary bevel. 
The universal bevel must be set and checked with 



2-10 




Figure 2-10. Universal vernier bevel protractor. 




28.317 



28.5 



Figure 2-11. Universal bevel. 



2-11 



Gear Tooth Vernier 
Cutter Clearance Gauge 

''' '' """ '""'- 



Adjustable Parallel 




Figure 2-12._Gear tooth vernier. 



28.318 



2-12 




28.7 



Figure 2-13. Cutter clearance gauge. 



minimum iimus. i ms msirumem, constructed to 
about the same accuracy of dimensions as parallel 
blocks, is very useful in leveling and positioning 
setups in a milling machine or in a shaper vise. 
An outside micrometer is usually used to set the 
adjustable parallel for height. 

Surface Gauge 

A surface gauge (fig. 2-15 is useful in gauging 
or measuring operations. It is used primarily in 
layout and alignment work. The surface gauge 
is commonly used with a scriber to transfer 
dimensions and layout lines. In some cases a dial 
indicator is used with the surface gauge to check 
trueness or alignment. 

FIXED GAUGES 

Fixed gauges cannot be adjusted. They can 
generally be divided into two categories, 
graduated and nongraduated. The accuracy of 
your work, when you use fixed gauges, will 
depend on your ability to determine the difference 
between the work and the gauge. For example, 
a skilled machinist can take a dimension 
accurately to within 0.005 of an inch or less when 




Figure 2-14. Adjustable parallel. 



28.6 



2-13 




SURFACE 
PLATE 



28.9 



Figure 2-15. Setting a dimension on a surface gauge. 



using a common rule. Practical experience in the 
use of these gauges will increase your ability to 
take accurate measurements. 

Graduated Gauges 

Graduated gauges are direct reading gauges in 
that they have scales inscribed on them enabling 
you to take a reading while using the gauge. The 
gauges in this group are rules, scales, thread 
gauges, and feeler gauges. 

RULES. The steel rule with holder set (fig. 
2-16A) is convenient for measuring recesses. It has 
a long tubular handle with a split chuck for 
holding the ruled blade. The chuck can be 
adjusted by a knurled nut at the top of the holder, 
allowing the rule to be set at various angles. The 
set has rules ranging from 1/4 to 1 inch in length. 

The angle rule (fig. 2-16B) is useful in 
measuring small work mounted between centers 
on a lathe. The long side of the rule (ungraduated) 
is placed even with one shoulder of the work. The 
graduated angle side of the rule can then be 
positioned easily over the work. 



Another useful device is the keyset rule (fig. 
2-16C). It has a straightedge and a 6-inch 
machinist 's-type rule arranged to form a right 
angle square. This rule and straightedge combina- 
tion, when applied to the surface of a cylindrical 
workpiece, makes an excellent guide for drawing 
or scribing layout lines parallel to the axis of the 
work. You will find this device very convenient 
when making keyseat layouts on shafts. 

You must take care of your rules if you 
expect them to give accurate measurements. Do 
not allow them to become battered, covered with 
rust, or otherwise damaged so that the markings 
cannot be read easily. Do not use them for 
scrapers, for once rules lose their sharp edges and 
square corners their general usefulness is 
decreased. 

SCALES. A scale is similar in appearance 
to a rule, since its surface is graduated into regular 
spaces. The graduations on a scale, however, 
differ from those on a rule because they are either 
larger or smaller than the measurements indicated. 
For example, a half-size scale is graduated so that 



2-14 



ANGLE RULE 




RULE WITH HOLDER 



CENTER 
LINE OF WORK 



KEYSEAT 
CLAMPS 



Figure 2-16. Special rules for shop use. 



28.10 



1 inch on the scale is equivalent to an actual 
measurement of 2 inches; a 12-inch long scale of 
this type is equivalent to 24 inches. A scale, 
therefore, gives proportional measurements 
instead of the actual measurements obtained with 
a rule. Like rules, scales are made of wood, 
plastic, or metal, and they generally range from 
6 to 24 inches. 

ACME THREAD TOOL GAUGE. This 

gauge (fig. 2-17) is used to both grind the tool used 
to machine Acme threads and to set the tool up 
in the lathe. The sides of the Acme thread have 
an included angle of 29 (14 1/2 to each side), 
and this is the angle made into the gauge. The 
width of the flat on the point of the tool varies 
according to the number of threads per inch. The 
gauge provides different slots for you to use as 
a guide when you grind the tool. Setting the tool 
up in the lathe is simple. First, ensure that the tool 
is centered on the work as far as height is 




5.16.1 



Figure 2-17. Acme thread gauges. 



2-15 



Til 1 1 II 1 1 II I A 




5.16.2 



Figure 2-18. Center gauge. 




Figure 2-19. Feeler (thickness) gauge. 



4.19 



concerned. Then, with the gauge edge laid parallel 
to the centerline of the work, adjust the side of 
your tool until it fits the angle on the gauge very 
closely. 

CENTER GAUGE. The center gauge (fig. 
2-18) is used like the Acme thread gauge. Each 
notch and the point of the gauge has an included 
angle of 60. The gauge is used primarily to check 
and to set the angle of the V-sharp and other 60 
standard threading tools. The center gauge is also 
used to check the lathe centers. The edges are 
graduated into 1/4, 1/24, 1/32, and 1/64 inch for 
ease in determining the pitch of threads on screws. 

FEELER GAUGE. A feeler (thickness) 
gauge, like the one shown in figure 2-19, is used 
to determine distances between two closely mating 
surfaces. This gauge is made like a jackknife with 
blades of various thicknesses. When you use a 
combination of blades to get a desired gauge 
thickness, try to place the thinner blades between 
the heavier ones to protect the thinner blades and 
to prevent their kinking. Do not force blades into 
openings which are too small; the blades may bend 
and kink. A good way to get the "feel" of using 
a feeler gauge correctly is to practice with the 
gauge on openings of known dimensions. 




28.338 



Figure 2-20. Fillet or radius gauges. 



28.11 



Figure 2-21. Straightedge. 



28.12 



Figure 2-22. Machinist's square. 



RADIUS GAUGE. The radius gauge (fig. 
2-20) is often underrated in its usefulness to the 
machinist. Whenever possible, the design of most 
parts includes a radius located at the shoulder 
formed when a change is made in the diameter. 
This gives the part an added margin of strength at 



2-16 




iwu euiuws, uuc uccu 



cnu, wmwu 



28.339 



Figure 2-23. Sine bars. 



that particular place. When a square shoulder is 
machined in a place where a radius should have 
been, the possibility that the part will fail by bend- 
ing or cracking is increased. The blades of most 
radius gauges have both concave (inside curve) and 
convex (outside curve) radii in the common sizes. 

Nongraduated Gauges 

Nongraduated gauges are used primarily as 
standards, or to determine the accuracy of form 
or shape. 

STRAIGHTEDGES. Straightedges look very 
much like rules, except that they are not graduated. 
They are used primarily for checking surfaces for 
straightness; however, they can also be used as 
guides for drawing or scribing straight lines. Two 
types of straightedges are shown in figure 2-21. 
Part A shows a straightedge made of steel which 
is hardened on the edges to prevent wear; it is the 
one you will probably use most often. The 
straightedge shown in Part B has a knife edge and 
is used for work requiring extreme accuracy. 



balance points. When a box is not provided, place 
resting pads on a flat surface in a storage area 
where no damage to the straightedge will occur 
from other tools. Then, place the straightedge so 
the two balance points sit on the resting pads. 

MACHINIST'S SQUARE. The most com- 
mon type of machinist's square has a hardened 
steel blade securely attached to a beam. The steel 
blade is NOT graduated. (See fig. 2-22.) This 
instrument is very useful in checking right angles 
and in setting up work on shapers, milling 
machines, and drilling machines. The size of 
machinist's squares ranges from 1 1/2 to 36 inches 
in blade length. You should take the same care 
of machinist's squares, in storage and use, as you 
do with a micrometer. 

SINE BAR. A sine bar (fig. 2-23) is a 
precision tool used to establish angles which 
required extremely close accuracy. When used in 
conjunction with a surface plate and gauge blocks, 
angles are accurate to 1 minute (1/60). The sine 
bar may be used to measure angles on work and 
to lay out an angle on work to be machined, or 
work may be mounted directly to the sine bar for 
machining. The cylindrical rolls and the parallel 
bar, which make up the sine bar, are all precision 
ground and accurately positioned to permit such 
close measurements. Be sure to repair any 
scratches, nicks, or other damage before you use 
the sine bar, and take care in using and storing 
the sine bar. Instructions on using the sine bar 
are included in chapter 3. 

PARALLEL BLOCKS. Parallel blocks (fig. 
2-24) are hardened, ground steel bars that are used 
in laying out work or setting up work for machin- 
ing. The surfaces of the parallel block are all either 



. 



28.319 



Figure 2-24. Parallel blocks. 

2-17 



pairs and in standard fractional dimensions. Use 
care in storing and handling them to prevent 
damage. If it becomes necessary to regrind the 
parallel blocks, be sure to change the size stamped 
on the ends of the blocks. 

GAUGE BLOCKS. Gauge blocks are used 
as master gauges to set and check other gauges 
and instruments. Their accuracy is from eight 
millionths (0.000008) of an inch to two millionths 
(0.000002) of an inch, depending on the grade of 
the set. To visualize this minute amount, consider 
that the thickness of a human hair divided 1 ,500 
times equals 0.000002 inch. This degree of accu- 
racy applies to the thickness of the gauge block, 
the parallelism of the sides, and the flatness of the 
surfaces. To attain this accuracy, a fine grade of 
hardenable alloy steel is ground and then lapped 
until the gauge blocks are so smooth and flat that 
when they are "wrung" or placed one atop the 
other in the proper manner, you cannot separate 
them by pulling straight out. A set of gauge blocks 
has enough different size blocks that you can estab- 
lish any measurement within the accuracy and 
range of the set. As you might expect, anything 
so accurate requires exceptional care to prevent 
damage and to ensure continued accuracy. A dust- 
free temperature-controlled atmosphere is pre- 
ferred. After use, wipe each block clean of all 
marks and fingerprints and coat it with a thin 
layer of white petrolatum to prevent rust. 

MICROMETER STANDARDS. Microm- 
eter standards are either disk- or tubular-shaped 
gauges that are used to check outside micrometers 
for accuracy. Standards are made in sizes so that 
any size micrometer can be checked. They should 
be used on a micrometer on a regular basis to 
ensure continued accuracy. Additional informa- 
tion for the use of the standards are given later 
in this chapter. 

RING AND PLUG GAUGES. A ring gauge 
(fig. 2-25) is a cylindrically-shaped disk that has 
a precisely ground bore. Ring gauges are used to 
check machined diameters by sliding the gauge 
over the surface. Straight, tapered, and threaded 
diameters can be checked by using the appropriate 
gauge. The ring gauge is also used to set other 
measuring instruments to the basic dimension 
required for their operation. Normally, ring 
gauges are available with a "GO" and a "NO 
GO" size that represents the tolerance allowed for 
the particular size or job. 



A. PLAIN CYLINDRICAL PLUG GAUGE 




GAUGE LINE 
TAPER PLUG GAUGE 




c. PLAIN CYLINDRICAL RING GAUGE 



GAUGE LINE 
0. TAPER RING GAUGE 



28.340 



Figure 2-25. Ring gauge and plug gauge. 



A plug gauge (fig. 2-25) is used for the same 
types of jobs as a ring gauge except that it is a 
solid shaft-shaped bar that has a precisely ground 
diameter for checking inside diameters or bores. 

THREAD MEASURING WIRES. The 

most accurate method of measuring the fit or 
pitch diameter of threads, without going into 
the expensive and sophisticated optical and 
comparator equipment, is thread measuring wires. 
The wires are accurately sized, depending on the 
number of threads per inch, so that when they 
are laid over the threads in a position that allows 
an outside micrometer to measure the distance 
between them, the pitch diameter of the threads 
can be determined. Sets are available that 
contain all the more common sizes. Detailed 
information on computing and using the wire 
method for measuring is covered in chapter 9. 

MICROMETERS 

Micrometers are probably the most often used 
precision measuring instruments in a machine 
shop. There are many different types, each 
designed to permit measurement of surfaces for 
various applications and configurations of 
workpieces. The degree of accuracy obtainable 
from a micrometer also varies, with the most 
common graduations being from one thousandth 
of an inch (0.001) to one ten-thousandth of an 
inch (0.0001). Information on the correct 



2-18 



_- ... -- . . - . . 

the more common types of micrometers is often called a micrometer caliper, or mike, is used 
provided in the following paragraphs. to measure the thickness or the outside diameter 




28.320 



Figure 2-26. Common types of micrometers. 
2-19 



U. "OLtltVt 




Figure 2-27. Nomenclature of an outside micrometer calipcr. 



28.321 



of parts. They are available in sizes ranging from 
1 inch to about 96 inches in steps of 1 inch. The 
larger sizes normally come as a set with inter- 
changeable anvils which provide a range of several 
inches. The anvils have an adjusting nut and a 
locking nut to permit setting the micrometer with 
a micrometer standard. Regardless of the degree 
of accuracy designed into the micrometer, the skill 
applied by each individual is the primary factor 
in determining accuracy and reliability in 
measurements. Training and practice will result 
in a proficiency in using this tool that will benefit 
you greatly. 

Inside Micrometer 

An inside micrometer (fig. 2-26) is used to 
measure inside diameters or between parallel 
surfaces. They are available in sizes ranging from 
0.200 inch to about 107 inches. The individual 
interchangeable extension rods that are assembled 
to the micrometer head vary in size by 1 inch. A 
small sleeve or bushing, which is 0.500 inch long, 
is used with these rods in most inside micrometer 
sets to provide the complete range of sizes. 
Using the inside micrometer is slightly more 
difficult than using the outside micrometer, 
primarily because there is more chance of your 



not getting the same "feel" or measurement each 
time you check the same surface. 

The correct way to measure an inside diameter 
is to hold the micrometer in place with one hand 
as you "feel" for the maximum possible setting 
of the micrometer by rocking the extension rod 
from left to right and in and out of the hole. 
Adjust the micrometer to a slightly larger 
measurement after each series of rocking 
movements until no rocking from left to right is 
possible and you feel a very slight drag on the in 
and out movement. There are no specific 
guidelines on the number of positions within a 
hole that should be measured. If you are check- 
ing for taper, you should take measurements as 
far apart as possible within the hole. If you are 
checking for roundness or concentricity of a hole, 
you should take several measurements at different 
angular positions in the same area of the hole. 
You may take the reading directly from the 
inside micrometer head, or you may use an out- 
side micrometer to measure the inside micrometer. 

Depth Micrometer 

A depth micrometer (fig. 2-26) is used to 
measure the depth of holes, slots, counterbores, 
recesses, and the distance from a surface to some 



2-20 



the closed end of the thimble. The measurement 
is read in reverse and increases in amount (depth) 
as the thimble moves toward the base of the 
instrument. The extension rods come either round 
or flat (blade-like) to permit measuring a narrow, 
deep recess or groove. 

Thread Micrometer 

The thread micrometer (fig. 2-26) is used to 
measure the depth of threads that have an 
included angle of 60. The measurement obtained 
represents the pitch diameter of the thread. They 
are available in sizes that measure pitch diameters 
up to 2 inches. Each micrometer has a given range 
of number of threads per inch that can be 
measured correctly. Additional information on 
using this micrometer can be found in chapter 9. 

Miscellaneous Micrometers 

The machine tool industry has been very 
responsive to the needs of the machinist by design- 
ing and manufacturing measuring instruments for 
practically every imaginable application. If you 
find that you are devising measuring techniques 
for a particularly odd application with the 
resulting measurements being of questionable 
value and that you do it on a routine basis, maybe 
a special micrometer will make your work easier 
and more reliable. Some of the special 
micrometers that you may have a need for are 
described below. 

BALL MICROMETER. This type microm- 
eter has a rounded anvil and a flat spindle. It can 
be used to check the wall thickness of cylinders, 
sleeves, rings, and other parts that have a hole 
bored in a piece of material. The rounded anvil 
is placed inside the hole and the spindle is bought 
into contact with the outside diameter. Ball 
attachments that fit over the anvil of regular out- 
side micrometers are also available. When using 
the attachments, you must compensate for the 
diameter of the ball as you read the micrometer. 

BLADE MICROMETER. A blade microm- 
eter has an anvil and a spindle that are thin and 
flat. The spindle does not rotate. This micrometer 
is especially useful in measuring the depth of 
narrow grooves such as an O-ring seat on an out- 
side diameter. 



IWU liai UJ31S.3. 1 11C UlMiUJUC UCIWCCII LUC 

increases as you turn the micrometer. It is used 
to measure the width of grooves or recesses on 
either the outside or the inside diameter. The 
width of an internal O-ring groove is an excellent 
example of a groove micrometer measurement. 

CARE AND MAINTENANCE 
OF GAUGES 

The proper care and maintenance of precision 
instruments is very important to a conscientious 
Machinery Repairman. To help you maintain 
your instruments in the most accurate and reliable 
condition possible, the Navy has established a 
calibration program that provides calibration 
technicians, the required standards and pro- 
cedures, and a schedule of how often an 
instrument must be calibrated to be reliable. When 
an instrument is calibrated, a sticker is affixed to 
it showing the date the calibration was done and 
the date the next calibration is due. Whenever 
possible, you should use the Navy calibration 
program to verify the accuracy of your instru- 
ments. Some repair jobs, due to their sensitive 
nature, demand the reliability provided by the 
program. Information concerning the procedures 
that you can use in the shop to check the accuracy 
of an instrument is contained in the upcoming 
paragraphs. 

Micrometers 

The micrometer is one of the most used, and 
often one of the most abused, precision measuring 
instruments in the shop. Careful observation of 
the do's and don'ts listed below will enable you 
to take proper care of the micrometer you use. 

1. Always stop the work before taking a 
measurement. Do NOT measure moving parts 
because the micrometer may get caught in the 
rotating work and be severely damaged. 

2. Always open a micrometer by holding the 
frame with one hand and turning the knurled 
sleeve with the other hand. Never open a 
micrometer by twirling the frame, because such 
practice will put unnecessary strain on the instru- 
ment and cause excessive wear of the threads. 

3. Apply only moderate force to the knurled 
thimble when you take a measurement. Always 
use the friction slip ratchet if there is one on the 
instrument. Too much pressure on the knurled 



2-21 



4. When a micrometer is not in actual use, 
place it where it is not likely to be dropped. 
Dropping a micrometer can cause the frame to 
spring; if dropped, the instrument should be 
checked for accuracy before any further readings 
are taken. 

5. Before a micrometer is returned to stowage, 
back the spindle away from the anvil, wipe all 
exterior surfaces with a clean, soft cloth, and coat 
the surfaces with a light oil. Do not reset the 
measuring surfaces to close contact because the 
protecting film of oil in these surfaces will be 
squeezed out. 

MAINTENANCE OF MICROMETERS. 

A micrometer caliper should be checked for zero 
setting (and adjusted when necessary) as a matter 
of routine to ensure that reliable readings are 
being obtained. To do this, proceed as follows: 

1 . Wipe the measuring faces, making sure that 
they are perfectly clean, and then bring the spindle 
into contact with the anvil. Use the same moderate 
force that you ordinarily use when taking a 
measurement. The reading should be zero; if it 
is not, the micrometer needs further checking. 

2. If the reading is more than zero, examine 
the edges of the measuring faces for burrs. Should 
burrs be present, remove them with a small slip 
of oilstone; clean the measuring surfaces again, 
and then recheck the micrometer for zero setting. 

3. If the reading is less than zero, or if you 
do not obtain a zero reading after making the 
correction described above, you will need to 
adjust the spindle-thimble relationship. The 
method for setting zero differs considerably 
between makes of micrometers. Some makes have 
a thimble cap which locks the thimble to the 
spindle; some have a special rotatable sleeve on 
the barrel that can be unlocked; and some have 
an adjustable anvil. 

Methods for Setting Zero. To adjust the 
THIMBLE-CAP TYPE, back the spindle away 
from the anvil, release the thimble cap with the 
small spanner wrench provided for that purpose, 
and bring the spindle into contact with the anvil. 
Hold the spindle firmly with one hand and rotate 
the thimble to zero with the other; after zero 
relation has been established, rotate the spindle 
counterclockwise to open the micrometer, and 
then tighten the thimble cap. After tightening the 



To adjust the ROTATABLE SLEEVE TYPE, 
unlock the barrel sleeve with the small spanner 
wrench provided for that purpose, bring the 
spindle into contact with the anvil, and rotate the 
sleeve into alignment with the zero mark on the 
thimble. After completing the alignment, back the 
spindle away from the anvil, and retighten the 
barrel sleeve locking nut. Recheck for zero setting, 
to be sure you did not disturb the thimble-sleeve 
relationship while tightening the lock nut. 

To set zero on the ADJUSTABLE ANVIL 
TYPE, bring the thimble to zero reading, lock the 
spindle if a spindle lock is provided, and loosen 
the anvil lock screw. After you have loosened the 
lock screw, bring the anvil into contact with the 
spindle, making sure that the thimble is still set 
on zero. Tighten the anvil setscrew lock nut 
slightly, unlock the spindle, and back the spindle 
away from the anvil; then lock the anvil setscrew 
firmly. After locking the setscrew, check the 
micrometer for zero setting to make sure you did 
not move the anvil out of position while you 
tightened the setscrew. 

The zero check and methods of adjustment of 
course apply directly to micrometers that will 
measure to zero; the PROCEDURE FOR 
LARGER MICROMETERS is essentially the 
same except that a standard must be placed 
between the anvil and the spindle in order to get 
a zero measuring reference. For example, a 2-inch 
micrometer is furnished with a 1-inch standard. 
To check for zero setting, place the standard 
between the spindle and the anvil and measure the 
standard. If zero is not indicated, the micrometer 
needs adjusting. 

Testing for and Correcting Errors By the Use 
Of Standards. A micrometer must be tested 
from time to time for uneven wear of measuring 
threads and for concave wear of the measuring 
faces because these defects are not detectable by 
zero-setting checks. The test for uneven internal 
wear can be made by measuring a flat-surfaced 
standard; the test for concavity of measuring 
faces, by measuring a cylindrical disk-shaped 
standard. 

The procedure for making these tests and 
correcting the defects which are found is as 
follows: First, check the micrometer for zero 
setting and adjust as necessary. Then take 
measurements of several different size gauge 
blocks or other accurate standards. If the 



2-22 



is muiuaieu, anu me nuuiuiiieiei 
be adjusted. Adjustment is made with the thread 
wear compensating nut, located inside the thimble 
assembly. After you complete the gauge block 
test, measure several cylindrical standards of 
different sizes. Discrepancies between micrometer 
readings and the marked (actual) sizes of the 
standards indicate that the measuring surfaces are 
concave. You can correct this condition by 
lapping the measuring faces on a true flat surface. 
After lapping the faces of the micrometer, reset 
the instrument for zero reading and measure the 
cylindrical standards again. 

Inside Micrometers. These instruments can 
be checked for zero setting adjusted in about the 
same way as a micrometer caliper; the main 
difference in the method of testing is that an 
accurate micrometer caliper is required for 
transferring readings to and from the standard 
when an inside micrometer is being checked. 

Micrometers of all types should be dis- 
assembled periodically for cleaning and lubrica- 
tion of internal parts. When this is done, each part 
should be cleaned in noncorrosive solvent, 
completely dried, and then given a lubricating coat 
of watchmaker's oil or a similar light oil. 

Vernier Gauges 

Vernier gauges also require careful handling 
and proper maintenance if they are to remain 
accurate. The following instructions apply to 
vernier gauges in general: 

1. Always loosen a gauge into position. 
Forcing, besides causing an inaccurate reading, 
is likely to force the arms out of alignment. 



neavy pressure win lorce me two scales oui 01 
parallel. 

3. Prior to putting a vernier gauge away, wipe 
it clean and give it a light coating of oil. (Perspira- 
tion from hands will cause the instrument to cor- 
rode rapidly.) 



Dials 

Dial indicators and other instruments that 
have a mechanically operated dial as part of their 
measurement features are easily damaged by 
misuse and lack of proper maintenance. The 
following instructions apply to dials in general: 

1 . As previously mentioned, be sure that the 
dial you have selected to use has the range 
capability required. When a dial is extended 
beyond its design limit, some lever, small gear or 
rack must give to the pressure. The dial will be 
rendered useless if this happens. 

2. Never leave a dial in contact with any 
surface that is being subjected to a shock (such 
as hammering a part when dialing it in) or an 
erratic and uncontrolled movement that could 
cause the dial to be overtraveled. 

3. Protect the dial when it is not being used. 
Provide a storage area where the dial will not 
receive accidental blows and where dust, oil, and 
chips will not contact it. 

4. When a dial becomes sticky or sluggish in 
operating, it may be either damaged or dirty. You 
may find that the pointer is rubbing the dial crystal 
or that it is bent and rubbing the dial face. Never 
oil a sluggish dial. Oil will compound the 
problems. Use a suitable cleaning solvent to 
remove all dirt and residue. 



2-23 



CHAPTER 3 

LAYOUT AND BENCHWORK 



As an MR 3 or MR 2 you will repair or assist 
in repairing a great many types of equipment used 
on ships. In addition to making replacement parts, 
you will disassemble and assemble equipment, 
make layouts of parts to be machined, and do 
precision work in fitting mating parts of equip- 
ment. This is known as benchwork and includes 
practically all repair work other than actual 
machining. 

This chapter contains information that you 
should know to enable you to make effective 
repairs to equipment. A brief discussion on 
blueprints and mechanical drawings is included 
because in many repair jobs you must rely heavily 
on information acquired from these sources. 
Other sources of information that you should 
study for details on specific equipment include the 
NA VSHIPS' Technical Manual, manufacturers' 
technical manuals, and training manuals that have 
information related to the equipment on which 
you are working. 



MECHANICAL DRAWINGS 
AND BLUEPRINTS 

A mechanical drawing, made with special 
instruments and tools, gives a true representation 
of an object to be made, including its shape, size, 
description, specifications of material to be used, 
and method of manufacture. A blueprint is an 
exact duplicate of a mechanical drawing. For 
reference purposes, every ship is furnished 
blueprint copies of all important mechanical 
drawings used in the construction of its hull and 
machinery. These blueprints are usually stowed 
in an indexed file in the log room, damage control 
office, technical library, or other central location, 
where they will be readily available for reference. 

The following paragraphs cover briefly some 
important points concerning working from 



sketches and blueprints. They do not contain 
definitions of all drafting terms, or information 
regarding the mechanics of blueprint reading, 
both of which are covered in detail in the training 
manual, Blueprint Reading and Sketching, 
NAVEDTRA 10077. 

Of the many types of blueprints you will use 
aboard ship, the simplest is the PLAN VIEW. 
This blueprint shows the position, location, and 
use of the various parts of the ship. You will use 
plan views to find your duty and battle stations, 
the sickbay, the barber shop, and other parts of 
the ship. 

In addition to plan views, you will find aboard 
ship other blueprints called assembly prints, unit 
or subassembly prints, and detail prints. These 
prints show various kinds of machinery and 
mechanical equipment. 

ASSEMBLY PRINTS show the various parts 
of a mechanism and how the parts fit together. 
Individual mechanisms, such as motors and 
pumps, will be shown on SUBASSEMBLY 
PRINTS. These show location, shape, size, and 
relationships of the parts of the subassembly unit. 
Assembly and subassembly prints are used to learn 
operation and maintenance of machines and 
equipment. 

Machinery Repairmen are most interested in 
DETAIL PRINTS; these will give you the 
information required to make a new part. They 
show size, shape, kind of material, and method 
of finishing. You will find them indispensable in 
your work. 



WORKING FROM DRAWINGS 

Detail prints usually show only the individual 
part that you must produce. They show two or 
more orthographic views of the object, and 



3-1 



8. 




lO 

N. 
I O 
: O 

O 
10 



^ M 



l; 81 



i 



*l 

& 

i S' 
y 

s 

: ' 

i i 

i *. 

c o 
a o 



eo 



2 

TJ 



Bf> 



3-2 



projection shows how the part will look when it 
is made. 



to figure 3-1 to see how each is used in blueprints. 



Each drawing or blueprint has a number in 
the title box in the lower right-hand corner of the 
print. The title box also shows the part name, scale 
used, pattern number, material required, assembly 
or subassembly print number to which the part 
belongs, and name or initials of the persons who 
drew, checked, and approved the drawings. (See 
fig. 3-1.) 

Accurate and satisfactory fabrication of a part 
described on a drawing depends upon how well 
the MR does the following: 

Correctly reads the drawing and closely 
observes all of its data. 

Selects the correct material. 

Selects the correct tools and instruments 
for laying out the job. 

Uses the baseline or reference line method 
of locating the dimensional points during layout, 
thereby avoiding cumulative errors (described 
later in this chapter). 

Strictly observes tolerances and 
allowances. 

Accurately gauges and measures the work 
throughout the fabricating process. 

Gives due consideration, when measuring, 
for expansion of the workpiece by heat generated 
by the cutting operations. This is especially 
important in checking dimensions during finishing 
operations, if work is being machined to close 
tolerance. 



COMMON BLUEPRINT SYMBOLS 

In learning to read machine drawings you 
must first become familiar with the common 
terms, symbols and conventions (general practice) 
that are normally used. The information in figures 
3-2, 3-3, and 3-4 will provide the basic data that 



Surface Texture 

Control over the finished dimensions of a part 
is no longer the only factor you must consider 
when deciding how you will do a job. The degree 
of smoothness, or surface roughness, has become 
very important in the efficiency and life of a 
machine part. 

A finished surface may appear to be perfectly 
flat; however, upon close examination with 
surface finish measuring instruments, the surface 
is found to be formed of irregular waves. On top 
of the waves are other smaller waves which we 
shall refer to as peaks and valleys. These peaks 
and valleys are used to determine the surface 
roughness measurements of height and width. The 
larger waves are measured to give the waviness 
height and width measurements. Figure 3-5 
illustrates the general location of the various areas 
for surface finish measurements and the relation 
of the symbols to the surface characteristics. 

Surface roughness is the measurement of the 
finely spaced surface irregularities, the height, 
width, direction, and shape of which establish the 
predominant surface pattern. The irregularities 
are caused by the cutting or abrading action of 
the machine tools that have been used to obtain 
the surface. One method of measuring the 
irregularities is by using special measuring 
instruments equipped with a tracer arm. The 
tracer arm has either a diamond or a sapphire 
contact point with a 0.0005-inch radius. As the 
tracer arm travels across the surface the contact 
point moves up and down the peaks and valleys. 
The movement of the contact point is amplified 
electrically and recorded graphically on a 
graduated tape. From this tape the various 
measurements are determined. 

The basic roughness symbol is a check mark. 
This symbol is supplemented with a horizontal 
extension line above it when requirements such 
as waviness width, or contact area must be 
specified in the symbol. A drawing that shows 
only the basic symbol indicates that the surface 
finish requirements are detailed in the Notes 
block. The roughness height rating is placed 
at the top of the short leg of the check 



3-3 



VISIBLE 
LINES 






HEAVY UNBROKEN LINES 

USED TO INDICATE VISIBLE 
EDGES OF AN OBJECT 






; 






























MEDIUM LINES WITH SHORT 
EVENLY SPACED DASHES 




1 
1 


i 
i 
i 






HIDDEN 
LINES 
























USED TO INDICATE CONCEALED 
EDGES 




r^ 


1_ 
























CENTER 
LIMES 






THIN LINES MADE UP OF LONG 
AND SHORT DASHES ALTERNATELY 
SPACED AND CONSISTENT IN 

LENGTH 

USED TO INDICATE SYMMETRY 
ABOUT AN AXIS AND LOCATION 
OF CENTERS 




^k 







3 

3 


DIMENSION 
LINES 




1 
I 


THIN L INES TERMIMATED WITH 
ARROW HEADS AT EACH END 

USED TO INDICATE DISTANCE 
MEASURED 




~~1 

r^ 





-* 
- 




























THIN UNBROKEN LINES 




- 




- 




LINES 






USED TO INDICATE EXTENT 
OF DIMENSIONS 































LEADER 


dl 


THIN LINE TERMINATED WITH ARROW. 
HEAD OR DOT ATONE END 

USED TO INDICATE A PART, 
DIMENSION OR OTHER REFERENCE 


r '. X 20 THD. 


y 




PHANTOM 
OR 
DATUM LINE 




MEDIUM SERIES OF ONE LONG DASH AND 
TWO SHORT DASHES EVENLY SPACED 
ENDING Wl TH L ONG DASH 

USED TO INDICAT E ALTERNATE POSITION 
OF PARTS, REPEAT ED DETAIL OR TO 
INDICATE A DATUM PLANE 


r 


BREAK 
(LONG) 


-V- 

-vy- 


THIN SOLID RUL ED LINES WITH 
FREEHAND ZIG-ZAGS 

USED TO REDUCE SIZE OF DRAWING 
REQUIRED TO DELINEATE OBJECT AND 
REDUCE DETAIL 




i \ i 


1 v 1 




BREAK 
(SHORT) 


1 


THICK SOL ID FREE HAND LINES 
USED TO INDICATE A SHORT BREAK 




~u 




CUTTINGOR 
VIEWING 
PLANE 


r i 

1 1 


THICK SOLID LINES WITH ARROWHEAD 
TO INDICATE DIRECTION IN WHICH 
SECTION OR PLANE IS VIEWED OR 
TAKEN 


EflTWTEl 


VIEWING 
PLANE 
OPTIONAL 


CUTTING 

PLANE FOR 
COMPLEX OR 

OFFSET 
VIEWS 


*-i 
i 
( % 

%v i 
i 
.4-j 


THICK SHORT DASHES 

USED TO SHOW OFFSET WITH ARROW. 
HEADS TO SHOW DIRECTION VIEWED 


-4", 

S^*~^fc*. P"/^ 

Ni./ \nm 

+ 



Figure 3-2. Line characteristics and conventions for MIL-STD drawing. 



3-4 



-^ 


ANGULARITY 




1 


PERPENDICULARITY 




II 


PARALLELISM 







CONCENTRICITY 




^ 


TRUE POSITION 







ROUNDNESS 




=- 


SYMMETRY 




(M) 


(MMO MAXIMUM MATERIAL 
CONDITION 


(RFS) REGARDLESS OF 
FEATURE SIZE 


B3 


DATUM IDENTIFYING 


SYMBOL 



Figure 3-3. Geometric characteristic symbols. 



\ 



-SYMBOL 
(THIS FEATURE 
SHALL BE 
PERPENDICULAR) 




A [ B 



MR 



DATUM 
REFERENCE 
(TO DATUM 
A) 



REFERENCE 

TO TWO 

TOLERANCE D**' 
(WITHIN .001 ' 
REGARDLESS OF 
FEATURE SIZE) 



J. A .001 



-B- 



Figure 3-4. Feature control symbol incorporating datum 
reference. 



rROUGHNESS HEIGHT 



TYPICAL FLAW 
(SCRATCH) 




WAV I NESS 
HEIGHT 
(INCHES) 



LAY (DIRECTION OF 
DOMINANT PATTERN) 



WAVINESS WIDTH 
(INCHES) 



SURFACE ROUGHNESS 
WIDTH 

ROUGHNESS -WIDTH 
CUTOFF (INCHES) 



WAVINESS 
HEIGHT (INCHES)' 

ROUGHNESS 
HEIGHT RATING 




WAVJNESS WIDTH (INCHES) 



ROUGH NESS -WIDTH CUTOFF 
(INCHES) 



LAY 

SURFACE ROUGHNESS WIDTH 




(INCHES) 



Figure 3-5. Relation of symbols to surface characteristics. 



3-5 



63 



63 



63 




Figure 3-6. Symbols used to indicate surface roughness, 
waviness, and lay. 



mium pciuussiuic luugmiess iicigiu ictimg; 

if two are shown, the top number is the 
maximum (part B, fig. 3-6). A point to 
remember is that the smaller the number 
in the roughness height rating, the smoother 
the surface. 

Waviness height values are shown directly 
above the extension line at the top of the 
long leg of the basic check (part C, fig. 
3-6). Waviness width values are placed just 
to the right of the waviness height values 
(part D, fig. 3-6). Where minimum requirements 



LAY SYMBOL 



DESIGNATION 



EXAMPLE 



LAY PARALLEL TO THE BOUNDARY LINE REPRESENT- 
ING THE SURFACE TO WHICH THE SYMBOL APPLIES. 




DIRECTION 

OF TOOL 

MARKS 



_L 



LAY PERPENDICULAR TO THE BOUNDARY LINE REPRE- 
SENTING THE SURFACE TO WHICH THE SYMBOL 
APPLIES. 



DIRECTION 

OF TOOL 

MARKS 



X 



LAY ANGULAR IN BOTH DIRECTIONS TO BOUNDARY 
LINE REPRESENTING THE SURFACE TO WHICH SYMBOL 
APPLIES. 



DIRECTION 

OF TOOL 

MARKS 



M 



LAY MULTIDIRECTIONAL 



C 



LAY APPROXIMATELY CIRCULAR RELATIVE TO THE 
CENTER OF THE SURFACE TO WHICH THE SYMBOL 
APPLIES. 




R 



LAY APPROXIMATELY RADIAL RELATIVE TO THE 
CENTER OF THE SURFACE TO WHICH THE SYMBOL 
APPLIES. 




P 



LAY PARTICULATE, NON-DIRECTIONAL, 
OR PROTUBERANT 




3 The "P" symbol is not currently shown in ISO Standards. American 
National Standards Committee B46 (Surface Texture) has proposed its 
inclusion in ISO 1302-"Methods of indicating surface texture on drawings." 

Figure 3-7. Symbols indicating the direction of lay. 



3-6 



\JJL Lilt 



E, fig. 3-6). Any further surface finish 
requirements that would have been shown 
in that location, such as waviness width 
or height, will be shown in the Notes block 
of the drawing. 

Lay is the direction of the predominant 
surface pattern produced by the tool marks. 
The symbol indicating lay is placed to the 
right and slightly above the point of the 
surface roughness symbol as shown in part 
F of figure 3-6. (Figure 3-7 shows the 
seven symbols that indicate the direction of 
lay.) 

The roughness width value is shown just to 
the right of and parallel to the lay symbol. The 
roughness width cutoff is placed immediately 
below the extension line and to the right of the 



In the past, an alpha-numeric symbol was used 
to indicate the degree of smoothness required on 
a part. This system was not very effective 
because no specific or measurable value was 
assigned to each classification of finish. A 
fine tool finish can mean different things 
to different people. Some of the more common 
symbols that may be found on older blueprints 
are shown in table 3-1. 

Your shop may not have the delicate and 
expensive instruments used to measure the 
irregularities of a surface although some of 
the larger and more fully equipped repair facilities 
will have them. There are roughness comparison 
specimens available today that will serve all 
but the most critical applications. These can be 
small plastic or metal samples, representing 
various roughness heights in several lay patterns. 



Table 3-1. Former Finish Designations 



Preferred 
Symbols 


Meaning 


Alternate Symbols 


F, 


Rough Tool Finish 


V, 


Fr. 


FIN. 


TF. 


F 2 


Fine Tool Finish 


V 2 


F. 


Fs. 


SF. 


F 3 


Grind Finish 


V 3 


Fg. 


Gr. 




F 4 


Polish 


V 4 


Bf. 


Buff 




F s 


Drill 


v s 


Dr. 






F 6 


Ream 


V 6 


Rm. 






F 7 


File Finish 


V 7 


ff. 


Ff. 




F 8 


Scrape 


V 8 


scr. 






F 9 


Spot Face 


V 9 








Finish All 
Over 






F.A.O. 




f.a.o. 



3-7 



Figure 3-8 gives a sampling of some roughness 
height values that can be obtained by the different 
machine operations that you will encounter. Use 
it as an estimating tool only, as it has the same 
shortcomings as the "F" values in table 3-1. 

UNITS OF MEASUREMENTS 

Accuracy is the trademark of the Machinery 
Repairman, and it is to your advantage to always 
strive for the greatest amount of accuracy. You 
can work many hours on a project and if it is not 
accurate, you will oftentimes have to start over. 
With this thought in mind, study carefully the 
following information about both the English and 
the metric systems of measurement. 

English System 

The inch is the basic (or smallest whole) unit 
of measurement in the English system. Parts of 
the inch must be expressed as either common 
fractions or decimal fractions. Examples of 



common fractions are 1/2, 1/4, 1/8, 1/16, 1/32, 
and 1/64. Decimal fractions can be expressed with 
a numerator and denominator (1/10, 1/100, 
1/1000, etc.,) but in most machine shop work and 
on blueprints or drawings they are expressed in 
decimal form such as 0.1, 0.01, and 0.001. 
Decimal fractions are expressed in the following 
manner: 

One-tenth inch = 0.1 in. 
One-hundredth inch = 0.01 in. 
One-thousandth inch = 0.001 in. 
One ten-thousandth inch = 0.0001 in. 

You will occasionally need to convert a 
common fraction to a decimal. This is easily 
done by dividing the denominator of the fraction 
into the numerator. As an example, the 
decimal equivalent of the fraction 1/16 inch 
is: 1 -r 16 = 0.0625 inch. A chart giving the 
decimal equivalents of the most common fractions 
is shown in Appendix I. 



MACHINE 
OPERATION 



ROUGHNESS HEIGHT (MICROINCHES) 
2000 1000 500 250 125 63 32 16 8 4 



FLAME CUTTING 



SAWING 
PLANING 



DRILLING 
MILLING 



BROACHING 
REAMING 
BORING, TURNING 



ROLLER BURNISHING 

GRINDING 

HONING 



POLISHING 
LAPPING 



SAND CASTING 




Figure 3-8. Roughness height values for machine operations. 



J. / ** Q -V 

this system of measurement. The basic unit of 
linear measurement for the metric system is the 
meter. 

In the metric system the meter can be sub- 
divided into the following parts: 

10 decimeters (dm) 

or 
100 centimeters (cm) 

or 
1000 millimeters (mm) 

Therefore, 1 decimeter is 1/10 of a meter, 1 
centimeter is 1/100 meter, and 1 millimeter is 
1/1000 meter. The metric unit of measurement 
most often used in the machinist trade is the 
millimeter (mm). 

If you understand the relationship of the 
two systems, you can convert easily from 
one system to the other. For example, 1 meter 
is equal to 39.37 inches; 1 inch is equal to 2.54 
centimeters (or 25.4 millimeters). To convert 
from the English system to the metric system, 
multiply the number of inches by 2.54 (for 
centimeters) or 25.40 (for millimeters). As an 
example: 1.375 inches converted to centi- 
meters is 1.375 inch x 2.540 = 3.4925 cm. 
Further, 0.0008 inch converted to millimeters 
is 0.0008 inch x 25.40 = 0.0203 mm. 

To convert from the metric system to the 
English system, divide the metric units of measure 
by either 2.54 (for centimeters) or 25.4 (for 
millimeters). As an example: 0.215 mm converted 
to inches is 0.215 mm -f 25.4 = 0.0084 inch. 

LIMITS OF ACCURACY 

You must work within the limits of accuracy 
specified on the drawing. A clear understanding 
of TOLERANCE and ALLOWANCE will help 
you to avoid making small, but potentially 
dangerous errors. These terms may seem closely 
related but each has a very precise meaning and 
application. In the following paragraphs we will 
point out the meanings of these terms and the 
importance of observing the distinction between 
them. 



addition to the basic dimensions, an allowable 
variation. The amount of variation, or limit of 
error permissible is indicated on the drawing as 
plus or minus () a given amount, such as 
0.005; 1/64. The difference between 
allowable minimum and the allowance maximum 
dimension is tolerance. For example, in figure 3-9: 

Basic dimension = 4 

Long limit = 4 1/64 
Short limit = 3 63/64 
Tolerance = 1/32 

When tolerances are not actually specified on 
a drawing, fairly concrete assumptions can be 
made concerning the accuracy expected, by using 
the following principles. For dimensions that end 
in a fraction of an inch, such as 1/8, 1/16, 1/32, 
1/64, consider the expected accuracy to be to the 
nearest 1/64 inch. When the dimension is given 
in decimal form, the following applies: 

If a dimension is given as 3.000 inches, the 
accuracy expected is 0.0005 inch; or if the 
dimension is given as 3.00 inches, the accuracy 
expected is 0.005 inch. The 0.0005 is called 
in shop terms, "plus or minus five ten- 
thousandths of an inch." The 0.005 is called 
"plus or minus five thousandths of an inch." 

Allowance 

Allowance is an intentional difference in 
dimensions of mating parts to provide the desired 
fit. A CLEARANCE ALLOWANCE permits 
movement between mating parts when they are 
assembled. For example, when a hole with a 
0.250-inch diameter is fitted with a shaft that has 
a 0.245-inch diameter, the clearance allowance is 
0.005 inch. An INTERFERENCE ALLOW- 
ANCE is the opposite of a clearance allowance. 



_ 

64 



Figure 3-9. Basic dimension and tolerance. 



3-9 



nidi nave ail miciiciciiLC auuwaucc. IL 

Si 0.251-inch diameter is fitted into the hole 
identified in the preceding example, the difference 
between the dimensions will give an interference 
allowance of 0.001 inch. As the shaft is larger than 
the hole, force is necessary to assemble the parts. 

What is the relationship between tolerance and 
allowance? In the manufacture of mating parts, 
the tolerance of each part must be controlled so 
that the parts will have the proper allowance when 
they are assembled. For example, if a hole 0.250 
inch in diameter with a tolerance of 0.005 inch 
(0.0025) is prescribed for a job, and a shaft to 
be fitted in the hole is to have a clearance 
allowance of 0.001 inch, the hole must first be 
finished within the limits and the required size of 
the shaft determined exactly, before the shaft can 
be made. If the hole is finished to the upper limit 
of the basic dimension (0.2525 inch), the shaft 
would be machined to 0.2515 inch or 0.001 inch 
smaller than the hole. If the dimension of the shaft 
were given with the same tolerance as the hole, 
there would be no control over the allowance 
between the parts. As much as 0.005-inch 
allowance (either clearance or interference) could 
result. 

To provide a method of retaining the required 
allowance while permitting some tolerance in the 
dimensions of the mating parts, the tolerance is 
limited to one direction on each part. This single 
direction (unilateral) tolerance stems from the 
basic hole system. If a clearance allowance is 
required between mating parts, the hole may be 
larger but not smaller than the basic dimension; 
the part that fits into the opening may be smaller, 
but not larger than the basic dimension. Thus, 
shafts and other parts that fit into a mating 
opening have a minus tolerance only, while the 
openings have a plus tolerance only. If an 
interference allowance between the mating parts 
is required, the situation is reversed; the opening 
can be smaller but not larger than the basic 
dimension, while the shaft can be larger, but not 
smaller than the basic dimension. Therefore you 
can expect to see a tolerance such as +0.005, - 0, 
or +0, -0.005, but with the required value not 
necessarily 0.005. One way to get a better 
understanding of a clearance allowance, or an 
interference allowance, is to make a rough sketch 
of the piece and add dimensions to the sketch 
where they apply. 



metal surfaces to provide an outline for 
machining. A layout is comparable to a single 
view (end, top, or side) of a part which is sketched 
directly on the workpiece. Any difficulty in 
making layouts depends on the intricacies of the 
part to be laid out and the number of operations 
required to make the part. A flange layout, for 
example, is relatively simple as the entire layout 
can be made on one surface of the blank flange. 
However, an intricate casting may require layout 
lines on more than one surface. This requires 
careful study and concentration to ensure that the 
layout will have the same relationships as those 
shown on the drawing (or sample) that you are 
using. 

When a part must be laid out on two or more 
surfaces, you may need to lay out one or two 
surfaces and machine them to size before using 
further layout lines. This prevents removal of 
layout lines on one surface while you are 
machining another. In other words, it would be 
useless to lay out the top surface of a part and 
machine off the layout lines while cutting the part 
to the layout lines of an end surface. 

Through the process of computing and 
transferring dimensions, you will become familiar 
with the relationship of the surfaces. Under- 
standing this relationship will benefit you in 
planning the sequence of machining operations. 

You should be able to hold the dimensions of 
a layout to within a tolerance of 1/64 inch. 
Sometimes you must work to a tolerance of even 
less than that. 

A layout of a part is made when the directional 
movement or location of the part is controlled by 
hand or aligned visually without the use of 
precision instruments (such as when work is done 
on bandsaws or drill presses.) In cutting irregular 
shapes on shapers, planers, lathes, or milling 
machines, layout lines are made, and the tool or 
work is guided by hand. In making a part with 
hand cutting tools, layout is essential. 

Mechanical drawing and layout are closely 
related subjects; knowledge of one will help you 
to understand the other. A knowledge of general 
mathematics, trigonometry, and geometry, as well 
as the selection and use of the required tools is 
necessary in doing jobs related to layout and 
mechanical drawing. Study Mathematics, Volume 
7, NAVEDTRA 10069; Mathematics, Volume II, 
NAVEDTRA 10071; Tools and Their Uses, 
NAVEDTRA 10085, and Blueprint Reading and 



3-10 



MATERIALS AND EQUIPMENT 

A scribed line on the surface of metal is usually 
hard to see; therefore, a layout liquid is used to 
provide a contrasting background. Commercially 
prepared layout dyes or inks are available through 
the Navy supply system. Chalk can be used, but 
it does not stick to a finished surface as well as 
layout dye. The commonly used layout dyes color 
the metal surface with a blue or copper tint. A 
line scribed on this colored surface reveals the 
color of the metal through the background. 

The tools generally used for making layout 
lines are the combination square set, machinist's 
square, surface gauge, scribe, straightedge, rule, 
divider, and caliper. Tools and equipment used 
in setting up the part to be laid out are surface 
plates, parallel blocks, angle plates, V-blocks, and 
sine bar. Surface plates have very accurately 
scraped flat surfaces. They provide a mounting 
table for the work to be laid out so that all lines 
in the layout can be made to one reference 
surface. Angle plates are used to mount the work 
at an angle to the surface plate. Angle plates are 
commonly used when the lines in the layout are 
at an angle to the reference surface. These plates 
may be fixed or adjustable; fixed angle plates are 
more accurate because one surface is machined 
to a specific angle in relation to the base. 
Adjustable angle plates are convenient to use 
because the angular mounting surface can be 
adjusted to meet the requirements of the job. V- 
blocks are used for mounting round stock on the 
surface plate. Parallel blocks are placed under the 
work to locate the work at a convenient height. 

The sine bar is a precision tool used for 
determining angles which require accuracy within 
5 minutes of arc. The sine bar may be used to 
check angles or to establish angles for layout and 
inspection work. The sine bar must be used in 
conjunction with a surface plate and gauge blocks 
if accuracy is to be maintained. Use of the sine 
bar will be covered later in this chapter. 

Toolmaker's buttons (figure 3-10) are hard- 
ened and ground cylindrical pieces of steel, used 
to locate the centers of holes with extreme 
accuracy. You may use as many buttons as 
necessary on the same layout by spacing them the 
proper distance from each other with gauge 
blocks. 

Many other special tools, which you may 
make, will be useful in obtaining layouts that are 



CAP SCREW 



BUTTON 



WORK 





Figure 3-10. Toolmaker's buttons and their application. 



accurate and easily done. Transfer screws and 
punches for laying out from a sample are two that 
you can use on many jobs and save time in doing 
the job. 

LAYOUT METHODS 

To ensure complete accuracy when making 
layouts, establish a reference point or line on the 
work. This line, called the baseline, is located so 
you can use it as a base from which to measure 
dimensions, angles, and lines of the layout. You 
can use a machined edge or centerline as a 
reference line. Circular layouts, such as flanges, 
are usually laid out from a center point and a 
diameter line. 

You can hold inaccuracy in layouts to a 
minimum by using the reference method because 
errors can be made only between the reference line 
and one specific line or point. Making a layout 
by referencing each line or point to the preceding 
one can cause you to compound any error, thus 
creating an inaccurate layout. 

Making a layout on stock that has one or more 
machine finished surfaces usually is easy. Laying 
out a casting, however, presents special problems 
because the surfaces are too rough and not true 
enough to permit the use of squares, surface 
plates, or other mounting methods with any 
degree of accuracy. A casting usually must be 
machined on all surfaces. Sufficient material must 
be left outside the layout line for truing up the 
surface by machining. For example, a casting 
might have only 1/8-inch machining allowance on 
each surface (or be a total of 1/4-inch oversize). 
It is obvious in this example that taking more than 
1/8 inch off any surface would mean the loss of 
the casting. The layout procedure is especially 



3-11 



must be within the machining allowance on all 
surfaces. 

Making Layout Lines 

The following information applies to practi- 
cally all layouts. Layout lines are formed by 
using a reference edge or point on the stock or 
by using the surface plate as a base. Study care- 
fully the section on geometric construction as this 
will aid you in making layouts when a reference 
edge of the stock or a surface plate mounting of 
the stock cannot be used. 

LINES SQUARE OR PARALLEL TO 

EDGES. When scribing layout lines on sheet 
metal, hold the scratch awl, or scribe, as shown 
in figure 3-11, leaning it toward the direction in 
which it will be moved and away from the 
straightedge. This will help scribe a smooth line 
which will follow the edge of the straightedge, 
template, or pattern at its point of contact with 
the surface of the metal. 

To scribe a line on stock with a combination 
square, place the squaring head on the edge of 





square with the edge of the stock against 
which the squaring head is held; that is, the 
angle between the line and the edge will be 
90. 

To draw lines parallel to an edge using a 
combination square, extend the blade from the 
squaring head the required distance, such as the 
2-inch setting shown in figure 3-13. Secure the 
blade at this position. Scribe a line parallel to the 
edge of the stock by holding the scratch awl, 01 
scribe, at the end of the blade as you move the 
square along the edge. All lines so scribed, with 
different blade settings, will be parallel to the edge 
of the stock and parallel to each other. 




Figure 3-13. Laying out parallel lines with a combinatioi 
square. 



Figure 3-11. Using a scribe. 





Figure 3-12. Using the combination square. 



Figure 3-14. Laying out a parallel line with a hermaphrodil 
caliper. 



3-12 



in figure 3-14, so the curved leg maintains 
contact with the edge while the other leg scribes 
the line. Hold the caliper so that the line will be 
scribed at the desired distance from the edge of 
the stock. 

FORMING ANGULAR LINES. To lay out 

a 45 angle on stock, using a combination square, 
place the squaring head on the edge of the stock, 
as shown in figure 3-15, and draw the line along 
either edge of the blade. The line will form a 45 
angle with the edge of the stock against which the 
squaring head is held. 

To draw angular lines with the protractor head 
of a combination square, loosen the adjusting 
screw and rotate the blade so the desired angle 




Figure 3-15. Laying out a 45 angle. 



PARALLEL 
UNES 



SCRIBER 



TRUE 
EDGE 




is 60. Tighten the screw to hold the setting. 

Hold the body of the protractor head in 
contact with the true edge of the work with the 
blade resting on the surface. Scribe the lines along 
the edge of the blade on the surface of the work. 
The angle set on the scale determines the angle 
laid out on the work. All lines drawn with the 
same setting, and from the same true edge of the 
work, will be parallel lines. 

Use the center head and rule as illustrated in 
figure 3-17 to locate the center of round stock. 
To find the center of square and rectangular 
shapes, scribe straight lines from opposite corners 
of the workpiece. The intersection of the lines 
locates the center. 

LAYING OUT CIRCLES AND IRREG- 
ULAR LINES. Circles or segments of circles are 
laid out from a center point. To ensure accuracy, 
prick-punch the center point to keep the point of 
the dividers from slipping out of position. 

To lay out a circle with a divider, take the 
setting of the desired radius from the rule, as 
shown in figure 3-18. Note that the 3-inch setting 




Figure 3-17. Locating the center of round stock. 




Figure 3-16. Laying out angular lines. 



Figure 3-18. Setting a divider to a dimension. 



3-13 



is being taken AWAY from the end of the rule. 
This reduces the chance of error as each point of 
the dividers can be set on a graduation. Place one 
leg of the divider at the center of the proposed 
circle, lean the tool in the direction it will be 
rotated, and rotate it by rolling the knurled 
handle between your thumb and index finger. (A 
of fig. 3-19.) 





Figure 3-21. Angle plate. 




Figure 3-19. Laying out circles. 




BULKHEAD 





SURFACE 
PLATE 



Figure 3-20. Laying out an irregular line from a surface. 



Figure 3-22. Setting and using a surface gauge. 



trammel points. 

To lay out a circle with trammel points, hold 
one point at the center, lean the tool in the 
direction you plan to move the other point, and 
swing the arc, or circle, as shown in B of figure 
3-19. 

To transfer a distance measurement with 
trammel points, hold one point as you would for 
laying out a circle and swing a small arc with the 
other point opened to the desired distance. 

Scribing an irregular line to a surface is a skill 
used in fitting a piece of stock, as shown in figure 
3-20, to a curved surface. In A of figure 3-20 you 
see the complete fit. In B of figure 3-20 the divider 
has scribed a line from left to right. When scribing 
horizontal lines, keep legs of the divider plumb 
(one above the other). When scribing vertical 
lines, keep the legs level. To scribe a line to an 
irregular surface, set the divider so that one leg 
will follow the irregular surface and the other leg 
will scribe a line on the material that is being fitted 
to the irregular surface. (See B of fig. 3-20.) 

USING THE SURFACE PLATE. The 

surface plate is used with such tools as parallels, 
squares, V-blocks, surface gauges, angle plates, 
and sine bar in making layout lines. Angle plates 
similar to the one shown in figure 3-21 are used 
to mount work at an angle on the surface plate. 
To set the angle of the angle plate, use a protractor 
and rule of the combination square set or use a 
vernier protractor. 

Part A of figure 3-22 shows a surface gauge 
V-block combination used in laying out a piece 
of stock. To set a surface gauge for height, first 



aa MIUWU ill Jj Ul llgluc 

3-22. Secure the scale so the end is in contact with 
the surface of the plate. Move the surface gauge 
into position. 

USING THE SINE BAR. A sine bar is a 
precisely machined tool steel bar used in 
conjunction with two steel cylinders. In the type 
shown in figure 3-23, the cylinders establish a 
precise distance of either 5 inches or 10 inches 
from the center of one to the center of the other, 
depending upon the model used. The bar itself 
has accurately machined parallel sides, and the 
axes of the two cylinders are parallel to the 
adjacent sides of the bar within a close tolerance. 
Equally close tolerances control the cylinder 
roundness and freedom from taper. The slots or 
holes in the bar are for convenience in clamping 
workpieces to the bar. Although the illustrated 
bars are typical, there is a wide variety of 
specialized shapes, widths, and thicknesses. 

The sine bar itself is very easy to set up and 
use. You do need to have a basic knowledge of 
trigonometry to understand how it works. When 
a sine bar is set up, it always forms a right triangle. 
A right triangle has one 90 angle. The base of 
the triangle, formed by the sine bar, is the surface 
plate, as shown in figure 3-23. The side opposite 
is made up of the gauge blocks that raise one end 
of the sine bar. The hypotenuse is always formed 
by the sine bar, as shown in figure 3-23. The 
height of the gauge block setting may be found 
in two ways. The first method is to multiply the 
sine of the angle needed by the length of the sine 
bar. The sine of the angle may be found in any 
table of natural trigonometric functions. For 



HYPOTENUSE 



SINE BAR 
(HYPOTENUSE) 



GAGE BLOCKS 
(SIDE OPPOSITE) 



GIVEN ANGLE 




SIDE ADJACENT 



SURFACE PLATE 
(SIDE ADJACENT) 



Figure 3-23. Setup of the sine bar. 



3-15 



LU a. LO.UIC ui iia.iuLd.1 LugunuuicuUr 

find the sine of 30 5'. Then multiply the sine value 
by 10 inches: 0.50126 x 10 = 5.0126, to find the 
height of the gauge blocks. The second method 
is to use a table of sine bar constants. These tables 
give the height setting for any given angle (to the 
nearest minute) for a 5-inch sine bar. Tables are 
not normally available for 10-inch bars because 
it is just as easy to use the sine of the angle and 
move the decimal point one place to the right. 
Although sine bars have the appearance of 
being rugged, they should receive the same care 
as gauge blocks. Because of the nature of their 
use in conjunction with other tools or parts that 
are heavy, they are subject to rough usage. 
Scratches, nicks, and burrs should be removed or 
repaired. They should be kept clean from abrasive 
dirt and sweat and other corrosive agents. Regular 
inspection of the sine bar will locate such defects 
before they are able to affect the accuracy of the 
bar. When sine bars are stored for extended 
periods, all bare metal surfaces should be cleaned 
and then covered with a light film of oil. Placing 
a cover over the sine bar will further prevent 
accidental damage and discourage corrosion. 

GEOMETRIC CONSTRUCTION OF LAY- 
OUT LINES. Sometimes you will need to scribe 
a layout that cannot be made using conventional 
layout methods. For example, you cannot readily 
make straight and angular layout lines on sheet 
metal with irregular edges by using a combination 
square set; neither can you mount sheet metal on 
angle plates in a manner that permits scribing 
angular lines. Geometric construction is the 
answer to this problem. 

Use a divider to lay out a perpendicular 
FROM a point TO a line, as shown in figure 3-24. 
Lightly prick-punch point C, then swing any arc 



auu jc/ as 



uwu cues 



at a point such as F. Place a straightedge on points 
C and F. The line drawn along this straightedge 
from point C to line AB will be perpendicular 
(90) to line AB. 

Use a divider to lay out a perpendicular 
FROM a point ON a line, as shown in figure 3-25. 
Lightly prick-punch the point identified in the 
figure as C on line AB. Then set the divider to 
any distance to scribe arcs which intersect AB at 
D and E with C as the center. Punch C and E 
lightly. With D and E used as centers and with 
the setting of the divider increased somewhat, 
scribe arcs which cross at points such as F and 
G. The line drawn through F and G will pass 
through point C and be perpendicular to line AB. 

To lay out parallel lines with a divider, set the 
divider to the selected dimension. Then referring 
to figure 3-26, from any points (prick-punched) 
such as C and D on line AB, swing arcs EF and 
GH. Then draw line IJ tangent to these two arcs 
and it will be parallel to line AB and at the selected 
distance from it. 

Bisecting an angle is another geometric 
construction with which you should be familiar. 
Angle ABC (fig. 3-27) is given. With B as a center, 
draw an arc cutting the sides of the angle at D 
and E. With D and E as centers, and with a radius 
greater than half of arc DE, draw arcs intersecting 
at F. A line drawn from B through point F bisects 
the angle ABC. 



Figure 3-25. Layout of a perpendicular from a point 
on a line. 



Figure 3-24. Layout of a perpendicular from a point 
to a line. 



AC D B 

Figure 3-26. Layout of a parallel line. 



3-16 




Figure 3-27. Bisecting an angle. 



Laying Out Valve Flange 
Bolt Holes 

Before describing the procedure for making 
valve flange layouts, we need to clarify the 
terminology used in the description. Figure 3-28 
shows a valve flange with the bolt holes marked 
on the bolt circle. The straight-line distance 
between the centers of two adjacent holes is called 
the PITCH CHORD. The bolt hole circle itself 
is called the PITCH CIRCLE. The vertical line 
across the face of the flange is the VERTICAL 
BISECTOR, and the horizontal line across the 
face of the flange is the HORIZONTAL 
BISECTOR. 



PITCH CIRCLE 



HORIZONTAL- 
BISECTOR 




VERTICAL 
BISECTOR 

PITCH CHORD 



SNUGLY FITTING 
WOOD PLUG 



Figure 3-28. Flange layout terminology. 



LIIC same as me 

chord between any other two adjacent holes. Note 
that the two top holes and the two bottom holes 
straddle the vertical bisector; the vertical bisector 
cuts the pitch chord for each pair exactly in half. 
This is the standard method of placing the holes 
for a 6-hole flange. In the 4-, 8-, or 12-hole flange, 
the bolt holes straddle both the vertical and 
horizontal bisectors. This system of hole place- 
ment permits a valve to be installed in a true 
vertical or horizontal position, provided, of 
course, that the pipe flange holes are also in 
standard location on the pitch circle. Before 
proceeding with a valve flange layout job, find 
out definitely whether the holes are to be placed 
in the standard position. If you are working on 
a "per sample" job, follow the layout of the 
sample. 

Assuming that you have been given informa- 
tion concerning the size and number of holes and 
the radius of the pitch circle, the procedure for 
setting up the layout for straight globe or gate 
valve flanges is as follows: 

1. Fit a fine grain wood plug into the 
opening in each flange. (See fig. 3-28.) The plug 
should fit snugly and be flush with the face of the 
flange. 

2. Apply layout dye to the flange faces, 
or, if dye is not available, rub chalk on 
the flange faces to make the drawn lines clearly 
visible. 

3. Locate the center of each flange with a 
surface gauge, or with a center head and rule 
combination, if the flange diameter is relatively 
small. (See part A fig. 3-22 and fig. 3-17.) 
After you have the exact center point located 
on each flange, mark the center with a sharp 
prick-punch. 

4. Scribe the pitch or bolt circle, using 
a pair of dividers. Check to see that the 
pitch circle and the outside edge of the flange are 
concentric. 

5. Draw the vertical bisector. This line 
must pass through the center point of the 
flange and must be visually located directly 
in line with the axis of the valve stem. 
(see fig. 3-28.) 



3-17 



6. Draw the horizontal bisector. This 
line must also pass through the center point 
of the flange and must be laid out at a 
right angle to the vertical bisector. (See fig. 3-28 
and fig. 3-25.) 

Up to this point, the layout is the same for 
all flanges regardless of the number of holes. 
Beyond this point, however, the layout differs 
with the number of holes. The layout for a 6-hole 
flange is the simplest one and will be described 
first. 

SIX-HOLE FLANGE. Set your dividers 
exactly to the dimension of the pitch circle radius. 
Place one leg of the dividers on the point where 
the horizontal bisector crosses the pitch circle on 
the right-hand side of the flange, point (1) in part 
A of figure 3-29, and draw a small arc across the 
pitch circle at points (2) and (6). Next, place one 
leg of the dividers at the intersection of the pitch 
circle and horizontal bisector on the left-hand side 
of the flange point (4), and draw a small arc across 
the pitch circle line at points (3) and (5). These 
points, (1 to 6), are the centers for the holes. 
Check the accuracy of the pitch chords. To do 
this, leave the dividers set exactly as you had them 
set for drawing the arcs. Starting from the located 
center of any hole, step around the circle with the 
dividers. Each pitch chord must be equal to the 
setting of the dividers; if it is not, you have an 



error in hole mark placement that you must 
correct before you center punch the marks 
for the holes. After you are sure the lay- 
out is accurate, center punch the hole marks 
and draw a circle of appropriate size around 
each center-punched mark and prick-punch 
"witness marks" around the circumference 
as shown in part B of figure 3-29. These 
witness marks will be cut exactly in half 
by the drill to verify a correctly located 
hole. 

FOUR-HOLE FLANGE. Figure 3-30 shows 
the development for a 4-hole flange layout. 
Set your dividers for slightly more than 
half the distance of arc AB, and then scribe 
an intersecting arc across the pitch circle 
line from points A, B, C, and D, as shown 
in part A of figure 3-30. Next, draw a 
short radial line through the point of inter- 
section of each pair of arcs as shown in 
part B. The points where these lines cross 
the pitch circle, (1), (2), (3), and (4), are 
the centers for the holes. To check the 
layout for accuracy, set your divider for 
the pitch between any two adjacent holes 
and step around the pitch circle. If the 
holes are not evenly spaced, find your error 
and correct it. When the layout is correct, follow 
the center-punching and witness-marking 
procedure described for the 6-hole flange layout. 



"WITNESS MARKS" 




Figure 3-29. Development of a 6-hole flange. 



me same memo a as aescnoea lor locaung poim 

(1) in the 4-hole layout. Then divide arc AE in 
half by the same method. The midpoint of arc 
AE is the location for the center of hole (1). (see 
part A of fig. 3-31.) Next, set your dividers for 
distance A (1), and draw an arc across the pitch 
circle line from A at point (8); from B at points 

(2) and (3); from C at (4) and (5); and from D 
at (6) and (7). (see part B of fig. 3-31.) 
Now set your calipers for distance AE and 



MATHEMATICAL DETERMINATION OF 
PITCH CHORD LENGTH. In addition to the 
geometric solutions given in the preceding 
paragraphs, the spacing of valve flange bolt hole 
centers can be determined by simple multiplica- 
tion, provided a constant value for the desired 
number of bolt holes is known. The diameter 
of the pitch circle multiplied by the constant 
equals the length of the pitch chord. The 




Figure 3-30. Four-hole flange development. 




Figure 3-31. Eight-hole flange development. 



3-19 



Here is an example of the use of the table. 
Suppose a flange is to have 9 bolt holes laid out 
on a pitch circle with a diameter of 10 inches. 
From the table, select the constant for a 9-hole 
flange. The pitch diameter (10 inches) multiplied 
by the appropriate constant (.342) equals the 
length of the pitch chord (3.420 inches). Set a pair 
of dividers to measure 3.420 inches, from point 
to point, and step off around the circumference 
of the pitch circle to locate the centers of the 
flange bolt holes. Note, however, that the actual 
placement of the holes in relation to the vertical 
and horizontal bisectors is determined separately. 
(This is of no concern if the layout is for an 
unattached pipe flange rather than for a valve 
flange.) 

BENCHWORK 

In this chapter, we will consider benchwork 
related to repair work, other than machining, in 
restoring equipment to an operational status. In 
repairing equipment, benchwork progresses in 
several distinct steps: obtaining information, 
disassembly of the equipment, inspection for 
defects, repair of defects, reassembly, and testing. 



Table 3-2. Constants for Locating Centers of Flange 
bolt Holes 



No. bolt holes 



9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 



Constant 



0.866 
.7071 
.5879 



.3827 
.342 



,2588 



,2079 

.195 

.184 



possible sources for this information. Job orders 
generally give brief descriptions of the equipment 
and the required repair. Manufacturers' technical 
manuals and blueprints give detailed information 
on operational characteristics and physical 
descriptions of the equipment. Operators can 
provide information on specific techniques of 
operation and may furnish clues as to why the 
equipment failed. The leading petty officer of 
your shop can provide valuable information on 
repair techniques, and can help you interpret the 
information. Use these sources of information to 
become familiar with the equipment before 
attempting the actual repair work. If you 
are thoroughly acquainted with the equipment, 
you will not have to rely on trial and error 
methods which are time consuming and some- 
times questionable in effectiveness. 

There are specific techniques that can be used 
in assembly and disassembly of equipment which 
will improve the effectiveness of a repair job. 
Whenever you repair equipment, you should note 
such things as fastening devices, fits between 
mating parts, and the uses of gaskets and packing. 
Noting the positions of parts in relation to mating 
parts or the unit as a whole is extremely helpful 
in ensuring that the parts are in correct locations 
and positions when the unit is reassembled. 

Inspecting the equipment before and during 
the repair procedure is necessary to determine 
causes of defects or damage. The renewal or 
replacement of a broken or worn part of a unit 
may give the equipment an operational status. 
Eliminating the cause of damage prevents 
recurrence. 

Repairs are made by replacement of parts, by 
machining the parts to new dimensions, or by 
using handtools to overhaul and recondition the 
equipment. Handtools are used in the repair 
procedure in jobs such as filing and scraping to 
true surfaces and in removing burrs, nicks, and 
sharp edges. 

It is often said that a repair job is incomplete 
until the repaired equipment has been tested for 
satisfactory operation. How equipment is tested 
depends on the characteristics of the equipment. 
In some cases testing facilities are available in the 
shop. When these facilities are not available, the 
unit may be placed back in operation and tested 
by normal use. 



3-20 



mucn ot me equipment tnat you are required to 
disassemble, repair, and reassemble. You must, 
therefore, use techniques that will aid you in 
remembering the position and location of parts 
in relatively intricate mechanisms. The following 
information applies in general to assembly and 
disassembly of any equipment. 

Equipment should be disassembled in a clean, 
well-lighted work area. With plenty of light, small 
parts are less likely to be misplaced or lost, and 
small but important details are more easily noted. 
Cleanliness of the work area, as well as the proper 
cleaning of the parts as they are removed, 
decreases the possibility of damage due to foreign 
matter when the parts are reassembled. 

Before starting any disassembly job, select the 
tools and parts you think you will need and take 
them to the work area. This will permit you to 
concentrate on the work without unnecessary 
interruptions during the disassembly and re- 
assembly processes. 

Have a container at hand for holding small 
parts to prevent their loss. Use tags or other 
methods of marking the parts to identify the unit 
from which they are taken. Doing this prevents 
mixing parts of one piece of equipment with parts 
belonging to another similar unit, especially if 
several pieces of equipment are being repaired in 
the same area. Use a scribe or prick-punch to 
mark the relative positions of mating parts that 
are required to mate in a certain position. (See 
fig. 3-32.) Pay close attention to details of the 
equipment you are taking apart and fix in your 
mind how the parts fit together. When you 



PUNCH 
MARKS 



JOINTS 




PUNCH 
MARKS 



Figure 3-32. Mating parts location marks. 



heavy pressure is required to separate parts. An 
overlooked pin, key, or setscrew that locks parts 
in place can cause extensive damage if pressure 
is applied to the parts. If hammers are required 
to disassemble parts, use a mallet or hammer with 
a soft face (lead, plastic, or rawhide) to prevent 
distortion of surfaces. If bolts or nuts or other 
parts are stuck together due to corrosion, use 
penetrating oil to free the parts. 



PRECISION WORK 

The majority of repair work that you perform 
will involve some amount of precision hand work 
of parts. Broadly defined, precision hand work 
to the Machinery Repairman can range from using 
a file to remove a burr or rough, sharp edge on 
a hatch dog to reaming a hole for accurately 
locating very close fitting parts. To accomplish 
these jobs, you must be proficient in the use of 
files, scrapers, precision portable grinders, thread 
cutting tools, reamers, broaches, presses and 
oxyacetylene torches. 



Scraping 

Scraping produces a surface that is more 
accurate in fit and smoother in finish than a 
surface obtained in a machining operation. It is 
a skill that requires a great deal of practice before 
you become proficient at it. Patience, sharp tools 
and a light "feel" are required to scrape a surface 
that is smooth and uniform in fit. 

Some of the tools you will use for scraping 
will be similar to files without the serrated 
edges. They are available either straight or 
with various radii or curves for scraping an 
internal surface at selected points. Other scraper 
tools may look like a paint scraper, possibly 
with a carbide tip attached. You may find that 
a scraper that you make from material in your 
shop will best suit the requirements of the job at 
hand. 

A surface plate and nondrying prussian blue 
are required for scraping a flat surface. Lightly 
coat the surface plate with blue and move the 
workpiece over this surface. The blue will stick 
to the high spots on the workpiece, revealing the 



3-21 



areas to be scraped. (See fig. 3-33.) Scrape the 
areas of the workpiece surface that are blue and 
check again. Continue this process until the blue 
coloring shows on the entire surface of the 
workpiece. To reduce frictional "drag" between 
mating finished scraped surfaces, rotate the solid 
surfaces so that each series of scraper cuts is made 
at an angle of 90 to the preceding series. This 
action gives the finished scraped surface a 
crosshatched or basket weave appearance. The 
crosshatched method also enables you to more 
easily see where you have scraped the part. 

A shell-type, babbitt-lined, split bearing or a 
bushing often requires hand scraping to ensure 
a proper fit to the surface that it supports or runs 
on. To do this, very lightly coat the shaft (or a 
mandrel the same size as the shaft) with nondrying 
Prussian blue. Turning the bearing on the shaft 
(or the mandrel in the bearing) just a short 
distance will leave thin deposits of the bluing on 
the high spots in the bearing babbitt. Then lightly 
scrape the high spots with a scraper shaped to 
permit selective scraping of the high spots without 
dragging along the other areas. Be very careful 
when doing this to prevent tapering the bearing 
excessively in either the longitudinal or radial 
direction. When you have worked out all the high 
spots, smooth out (or replace if necessary) the 
bluing on the shaft or mandrel and repeat the 
process until you have produced an acceptable 
seating pattern. This job cannot be rushed and 
done properly at the same time. A poor seating 
pattern on a bearing could lead to an early failure 
when the bearing is placed into service. 

Removal of Burrs and Sharp Edges 

One of the most common injuries that occurs 
in machine shops is a cut or scratch caused by a 




Figure 3-33. Checking a surface. 



sharp edge on a part. When a pump or other piece 
of machinery that has been overhauled binds or 
wipes with little or no operating time, an investiga- 
tion will often reveal a sharp edge that has peeled 
or broken off and jammed into an area that has 
very little clearance. In spite of this and 
other instances that cause either discomfort or 
additional work, the removal of burrs and sharp 
edges is often overlooked by the machinist. Close 
examination of the old part or the blueprint will 
sometimes indicate that a machined radius is 
required. Regardless of the design or use of a part, 
a few seconds in removing these sharp edges with 
a file is time well spent. 

Hand Reaming 

When you need a round hole that is accurate 
in size and smooth in finish, reaming is the process 
that you will probably select. There are two types 
of reaming processes machine reaming and hand 
reaming. Machine reaming requires a drill press, 
lathe, milling machining or other power tool to 
hold and drive either the reamer or the part. 
Machine reaming will be covered in chapter 8. 
Hand reaming is more accurate and is the method 
you will probably use most in precision 
bench work. 

A hand reamer has a straight shank and a 
square machined on its end. It is driven by hand 
with a tap wrench placed on the square end. 
Several different types of hand reamers are 
available, as shown in figure 3-34. Each of the 
different types has an application for which it is 
best suited and a limiting range or capability. The 
solid hand reamer in part A of figure 3-34 is used 
for general purpose reaming operations where a 
standard or common fractional size is required. 
It is made with straight, helical, or spiral flutes. 
A helical fluted reamer is used when an 
interrupted cut, such as a part with a key way 
through it, must be made. The helical flutes ensure 
a greater contact area of the cutting edges than 
the straight fluted reamer, preventing the reamer 
from hanging up on the keyway and causing 
chatter, oversizing and poor finishes. 

The expansion reamer in B of figure 3-34 is 
available as either straight or helical fluted. These 
reamers are used when a reamed hole slightly 
larger than the standard size is required. 
Expansion reamers can be adjusted from about 
0.006 inch larger for a 1/4-inch reamer to about 
0.012 inch larger for a 1 1/2-inch reamer. The 
adjustment is made by turning the screw on the 
cutting end of the reamer. 



SOLID HAND REAMER 



D 



B 



TAPER PIN REAMER 



EXPANSION REAMER SOLID 




TAPER PIPE REAMER 






EXPANSION REAMER INSERTED TOOTH 

Figure 3-34. Hand reamers. 



The expansion reamer in C of figure 3-34 has 
a much greater range for varying its size. Each 
reamer is adjustable to allow it to overlap the 
smallest diameter of the next larger reamer. The 
cutting blades are the insert type and can be 
removed and replaced when they become dull. 
Adjustment is made by loosening and tightening 
the two nuts on each side of the blades. 

The taper pin reamer in D of figure 3-34 has 
a taper of 1/4 inch per foot and is used to ream 
a hole to accept a standard size taper pin. This 
reamer is used most often when two parts require 
a definite alignment position. When drilling the 
hole for this reamer, it is often necessary to step 
drill through the part with several drills of 
different sizes to help reduce the cutting pressure 
put on the reamer. Charts which give the 
recommended drill sizes are available in several 
machinist reference books. In any case, the 
smallest drill used cannot be larger than the small 
diameter of the taper pin. 

The taper pipe reamer in E of figure 3-34 has 
a taper of 3/4 inch per foot and is used to prepare 
a hole that is to be threaded with a tapered pipe 
thread. 

The size of the rough drilled or bored hole to 
be hand reamed should be between 0.002 inch and 
about 0.015 inch (1/64) smaller than the reamer 
size. A smoother and more accurately reamed hole 
can be produced by keeping to a minimum the 



amount of material that a reamer is to remove. 
You must be careful to keep the rough hole from 
being oversized or out-of-round. This is a very 
common problem in drilling holes, and you can 
prevent it only by using a correctly sharpened drill 
under the most closely controlled conditions 
possible. Information on drilling can be found in 
chapter 5. 

Alignment of the reamer to the rough hole is 
a critical factor in preventing oversized, out-of- 
round or bell-mouthed holes. If possible, perform 
the reaming operation while the part is still set 
up for the drilling or boring operation. Insert a 
center in the spindle of the machine and place it 
in the center hole in the shank of the reamer to 
guide the reamer. 

Another method of alignment is to fabricate 
a fixture with guide bushings made from bronze 
or a hardened steel to keep the reamer straight. 
When a rough casting or a part that has the 
reamed hole at an angle to its surface must be 
reamed, it is best to spot face or machine the area 
next to the hole so that the hole and the surface 
are perpendicular. This will prevent an uneven 
start and possibly reamer breakage. In most 
reaming operations, you will find that the use of 
a lubricant will give a better reamed hole. The 
lubricant or cutting fluid helps to reduce heat and 
friction and washes away the ships that build up 
on the reamer. Soluble oil will normally serve very 



3-23 



well; however, in some cases, a lard or sulfurized 
cutting oil may be required. When the reaming 
operation is complete, remove the reamer from 
the part by continuing to turn the reamer 
in the same direction (clockwise) and putting 
a slight upward pressure on it with your hand 
until it has cleared the hole completely. Reversing 
the direction of the reamer will probably 
result in damage to both the cutting edges and the 
hole. 

A straight hand reamer is generally tapered on 
the beginning of the cutting edges for a distance 
approximately equal to the diameter of the 
reamer. You will have to consider this when you 
ream a hole that does not go all the way through 
a part. 

Broaching 

Broaching is a machining process that cuts or 
shears the material by forcing a broach through 
the part in a single stroke. A broach is a tapered, 
hardened bar, into which have been cut teeth that 
are small at the beginning of the tool and get 
progressively larger toward the end of the tool. 
The last several teeth will usually be the correct 
size of the desired shape. Broaches are available 
to cut round, square, triangular and hexagonal 
holes. Internal splines and gears and key ways can 
also be cut using a broach. A key way broach 
requires a bushing that will fit snugly in the hole 
of the part and has a rectangular slot in it to slide 
the broach through. Shims of different thicknesses 
are placed behind the broach to adjust the depth 
of the key way cut (fig. 3-35). 

A broach is a relatively expensive cutting tool 
and is easily rendered useless if not used and 
handled properly. Like all other cutting tools, it 
should be stored so that no cutting edge is in 
contact with any object that could chip or dull 
it. Preparation of the part to be broached is as 
important as the broaching operation itself. The 
size of the hole should be such that the beginning 
pilot section enters freely but does not allow the 
broach to freely fall past the first cutting edge or 
tooth. If the hole to be broached has flat sides 
opposite each other, you need only to measure 
across them and allow for some error from drill- 
ing. The broach will sometimes have the drill size 
printed on it. Be sure the area around the hole 
to be broached is perpendicular on both the 
entry and exit sides. 

Most Navy machine shop applications involve 
the use of either a mechanical or a hydraulic press 
to force the broach through the part. A 



considerable amount of pressure is required to 
broach, so be sure that the setup is rigid and that 
all applicable safety precautions are strictly 
observed. A slow even pressure in pushing the 
broach through the part will produce the most 
accurate results with the least damage to the 
broach and in the safest manner. Do not bring 
the broach back up through the hole, push it on 
through and catch it with a soft cushion of some 
type. A lubricant is required for broaching most 
metals. A special broaching oil is best; however, 
lard oil or soluble oil will help to cool the tool, 
wash away chips and prevent particles from gall- 
ing or sticking to the teeth. 

Hand Taps and Dies 

Many of the benchwork projects that you do 
will probably have either an internally or an 
externally threaded part in the design specifica- 
tions. The majority of the threads cut on a bench- 
work project are made with either hand taps, for 
internally threaded parts, or hand dies for 
externally threaded parts. The use of these two 
cutting tools has come to be considered as a simple 
skill requiring little or no knowledge of the tools 
and no preplanning of the operation to be 
performed. It is true that the operations are 
simple, but only after several factors concerning 
the correct selection and use of the tools have been 
studied and practiced. Taps and dies are fast and 
accurate cutting tools that can make a job much 
easier and will produce an excellent end product. 
The information given in the following 
paragraphs will provide the general knowledge 
and operational factors to start you in the 
correct use of taps and dies. 

TAPS. Hand taps (fig. 3-36) are precision 
cutting tools which usually have three or four 
flutes and a square on the end for placing a tap 
wrench to turn the tap. Taps are made from either 
hardened carbon steel or high-speed steel and are 
very hard and brittle. They are easily broken or 
damaged when treated roughly or forced too 
quickly through a hole. 

Taps for most of the different thread forms, 
described later in this manual, are available either 
as a standard stock item or catalog special ordered 
from a tap manufacturer. The information in this 
section concerns only the most commonly used 
thread forms, the Unified thread and the 
American National thread. Both of these thread 
systems have a 60-degree included angle or V 
form. 




28.33 



Figure 3-35. Broaching a keyway on a gear. 




V 8 -I6 NC 
G H4 



TAPER 



__D V'6NC C ........- 

6 H4 IHUlllUni 




PLUG 



_-^^vw^AA^^^^^^^v^A^vvvi^ 




BOTTOMING 



Figure 3-36. Set of taps. 



Taps usually come in a set of three for each 
different diameter and number of threads per 
inch. A taper, or starting tap (fig. 3-36), has 8 to 
10 of the beginning teeth that are tapered. The 
taper allows each cutting edge or tooth to cut 
slightly deeper than the one before it. This permits 
an easier starting for the tap and exerts a 
minimum amount of pressure against the tool. 
The next several teeth after the taper ends are at 
the full designed size of the tap. They remove only 
a small amount of material and help to leave a 
fine finish on the threads. The last few teeth have 
a very slight back taper that allows the tap to clear 
the final threads cut without rubbing or binding. 
The plug tap has 3 to 5 of the beginning teeth 
tapered and the remaining length has basically the 
same design as the taper tap. The bottoming tap 



3-25 



by the tapered teeth, it is always advisable to begin 
the tapping operation with the taper, or starting 
tap. If the hole being tapped goes all the way 
through the material, the taper tap is usually the 
only one required. If the hole is a blind one, or 
does not go all the way through the material, all 
three taps will be required. The taper tap will be 
used first, followed by the plug tap, and the final 
pass will be made with the bottoming tap. 

Standard Sizes and Designations. The size 
of a tap is marked on the shank or the smooth 
area between the teeth and the square on the end. 
The numbers and letters always follow the same 
pattern and are simple to understand. As an 
example, the marking 3/8 - 16 NC (fig. 3-36) 
means that the diameter of the tap is 3/8 inch and 
that it has 16 threads per inch. The NC is a sym- 
bol indicating the thread series. In this case, the 
NC stands for the American National Coarse 
Thread Series. 

Some additional common thread series 
symbols are NF, American National Fine; NS, 
American National Special; NEF, American 
National Extra Fine; and NPT, American 
National Standard Tapered pipe. A "U" placed 
in front of one of these symbols indicates the 
UNIFIED THREAD SYSTEM, a system that has 
the same basic form as the American National and 
is interchangeable with it, differing mainly in 
tolerance or clearance. These thread systems will 
be covered in more detail in chapter 9. If an LH 
appears on the marking after the thread series 
symbols, the tap is left-handed. 

The next group of markings usually found on 
taps refers to the method of producing the threads 
on the tap and the tolerance of the tap. As an 
example, in the marking G H4 (fig. 3-36) the G 
indicates that the threads were ground on the tap. 
The greatest majority of the taps manufactured 
today are ground. The next symbol, H4, refers 
to the tolerance of the tap. The H means that the 
tap has a pitch diameter that is above (HIGH) the 
basic pitch diameter for that size tap. An L means 
that the pitch diameter is under (LOW) the basic 
pitch diameter for that size tap. The number 
following the H or L indicates the amount of 
tolerance in increments of 0.0005 inch. In the 
example H4, the pitch diameter is a maximum of 
0.002 inch (4 x 0.0005) above the basic pitch 
diameter. In the case of an L, the amount is under 
the basic pitch diameter. A number of 1 through 
10 can be found on taps. This tolerance limit 



classes will be covered later in this manual. 

The only difference in the size and designation 
markings for taps that will probably be found in 
Navy machine shops is in machine screw diameter 
taps, or numbered taps, as they are often called 
in the shop. Instead of the diameter being 
represented by a fraction, a number of through 
14 is used. You can easily convert these numbers 
to a decimal equivalent by remembering that the 
number tap has a diameter of 0.060 inch and 
each tap number after that increases in diameter 
by 0.013 inch. As an example: 

Size = 0.060 inch dia. 

Size 3 = 0.099 inch dia. [0.060 + 3 x 0.013] 

Size 14 = 0.242 inch dia. [0.060 + 14 x 0.0131 

A typical marking on a tap might be 10.24 UNC, 
indicating a diameter of 0.190 inch, 24 threads 
per inch, and a Unified National Coarse thread 
series. 

Tapping Operations. The first step in any 
successful tapping operation is the selection of the 
correct size tap with sharp, unbroken cutting edges 
on the teeth. A dull tap will require excessive force 
to produce the threads and increases greatly the 
chance of the tap breaking and damaging the part 
being tapped. A dull tap can also produce ragged, 
torn and undersize threads, leading to a damaged 
part. 

The tap drill or the size of the hole that is made 
for the tap is very important if the correct fit is 
to be obtained. If a hole were to be drilled equal 
in size to the minor, or smallest, diameter of the 
tap, a 100% thread height would result. To tap 
a hole this size would require excessive pressure 
and breakage could occur, especially with a small 
tap or a material that is hard. Unless a blueprint 
or other design references indicate differently, a 
15% thread height is usually considered adequate 
and is actually only about 5% less in terms of 
strength or holding power than a 100% thread 
height. In some of the less critical jobs, it is 
possible to have a 60% thread height without a 
significant loss in strength. 

There are two simple formulas that you may 
use to calculate the tap drill size for any size tap. 
The simplest and the one most often used will 
produce a thread height of approximately 75%. 



3-26 



(DS = TD - ). As an example, the drill 
size for a 1/4 - 20 NC tap is required as follows: 

Step 1: DS= 1/4 - 1/20 
Step 2: DS = 0.250 - 0.050 
Step 3: DS = 0.200 in. 

The nearest standard size drill would then be 
selected to make the hole. In this case, a number 

8 drill has a diameter of 0. 199 inch and a number 
7 drill has a diameter of 0.201 inch. Unless the 
size differences are very great, it is more effective 
to select the larger drill size or the number 7 drill 
for this tap. 

The second formula, although slightly more 
difficult, allows for a selection of the desired 
percentage of thread height. To use it, you must 
know the straight depth of the thread. You can 
obtain this data from various charts in handbooks 
for machinists or by using the formulas in chapter 

9 of this manual. It is as follows: DRILL 
SIZE = TAP DIAMETER MINUS THE 
DESIRED PERCENTAGE OF THREAD 
HEIGHT TIMES TWICE THE STRAIGHT 
DEPTH. As an example, if 60% thread height 
is desired for a 1/4 - 20 NC tap, the drill size is 
figured as follows: 

Step 1: DS = 1/4 - .60 x 2(0.032) 
Step 2: DS = 0.250 - .60 x 0.064 
Step 3: DS = 0.250 - 0.038 
Step 4: DS = 0.212 in. 

The nearest standard size drill to 0.212 inch is a 
number 3 drill which has a diameter of 0.213 inch. 
A word of caution about drilling holes for tapping 
is important at this point. Even if the drill is 
ground perfectly, the part is rigidly clamped and 
the drilling machine has no looseness, the drilled 
hole can be expected to be oversized. In the case 
of the number 7 and the number 3 drills selected 
in the two examples given, the drilled holes will 
probably be approximately 0.003 to 0.004 inch 
oversize. You should consider this in planning the 
operation. Additional information on drilling 
holes is in chapter 5. 



and shape. You MUST be sure that the part can- 
not vibrate loose and be thrown out of the vise 
or off of the drill press table. When a twist drill 
driven by a geared motor digs in or binds in a part, 
a great amount of force is exerted against the part. 
You could lose a finger or hand, break a leg, or 
worse if this happens. It is best to start the drilling 
operation with a small drill or a center drill 
(described later in this manual) by aligning the 
drill point as close as possible to the center punch 
mark you made to locate the center of the hole. 
When you have done this, insert the tap drill 
into the drilling machine or drill press and drill 
the hole. If the hole is very large, use a drill several 
sizes below the tap drill size to prevent an out- 
of-round or excessively oversized hole. Do NOT 
move the part when you make the various tool 
changes. 

The hole is now ready to be tapped. Some taps 
have a center hole in the shank that will fit over 
the point of a center. If this is the case and the 
setup will allow it, place a center in the drill press 
without moving the part; place a tap wrench over 
the square shank, turn the center into the center 
hole on the tap wrench over the square shank, (fig. 
3-37) and slowly turn the tap while applying a 



CHUCK 



CENTER 




WORK 



TAPPING WORK IN 
A DRILL PRESS 



TAP 




SQUARE 



WORK 



CHECKING TAP 
WITH A SQUARE 



Figure 3-37. Starting a tap. 



3-27 



slight downward pressure on the center to help 
guide the tap. If a center cannot be used, align 
the tap as close as possible by eye and make 2 or 
3 turns with the tap handle. Remove the tap 
handle and place a good square on the surface 
of the part (if the part is machined flat) and bring 
the square into contact with one set of teeth. Do 
the same check on the next set of teeth in either 
direction around the tap (fig. 3-37). If the tap is 
not perpendicular or square with the surface at 
both points, back it out and start over. When the 
tap is square, begin turning the tap wrench slowly. 
After making two or three turns, turn the tap 
backwards to break the chips and help clear them 
from the path of the tap. Proceed with this until 
the tap bottoms out; then place the next tap in 
the set in the hole and repeat the tapping 
procedure. If the hole is blind, remove the taps 
often to clear the chips from the bottom. 

It is often necessary to remove burrs from 
around a hole that has been tapped. Do this with 
a file, by slowly hand-spinning a larger twist drill 
in the hole, or by using a countersink. 

A cutting oil should be used in most tapping 
operations. There are several commercial products 
available that greatly enhance the quality of thread 
produced. A heavy cutting oil with either a sulfur, 
mineral oil or lard oil base is available in the 
supply system. If no other cutting oil is available, 
a heavy mixture of soluble oil is acceptable. 

DIES. Hand threading dies come in various 
styles, including unadjustable solid square and 
round shaped dies and adjustable single and two- 
piece dies. The most common die used in Navy 
machine shops is the adjustable single piece or 
round split die (fig. 3-38). The adjustable round 
split die is a round disk-shaped tool which has 
internal threads and usually four holes or flutes 
that interrupt the threads and present four sets 
of cutting edges. The die has a groove cut 
completely through one side and a setscrew to 
allow for a small amount of expansion and 
contraction of the die. This feature permits an 
adjustment for taking a rough and a finish cut 
on particularly hard or tough metals and also 
allows for slight adjustments to obtain a close fit 
with a mated nut or other internally threaded part. 
There is a difference in the two sides of the die 
the starting side has about 3 full threads tapered 
and the trailing side has about 1 thread tapered. 
To prevent damage to the die and the threads 
being cut, the die should always be started with 
the greatest taper leading. The die is held in a 
diestock (fig. 3-38), a tool which has a circular 




ADJUSTING 
SCREW 

ROUND SPLIT DIE 
A 



LOCKING 
HOLE 




THREE SCREW DIESTOCK 

B 
Figure 3-38. Die and diestock. 



recess to hold the die and three setscrews that fit 
into small indentations in the outside diameter of 
the die. 

The size of a die is usually marked on the trail- 
ing face (the side that is up during threading) and 
follows the same format as a tap. A die marked 
5/8-11 NC will cut a thread that has a 
5/8-inch diameter and 11 American National 
Coarse threads per inch. The G, H, L, and 
associated numbers found on a tap are not 
normally marked on a die because they represent 
a fixed tolerance and the die is adjustable. 

The steps involved in threading a part with a 
die are similar to those for a tap. The part to be 
threaded should have a chamfer ground or cut on 
the end to help in starting the die squarely with 
the part. Select the correct die and insert it in the 
diestock with the longest tapered side opposite the 
square shoulder. Apply cutting oil and place the 
die over the part by grasping the diestock in the 
middle with one hand. Turn the die several turns, 
then look carefully at the die and the part to 
ensure that they are square to one another. 
Threads that are deeper on one side than the other 
indicate a misaligned die. Turn the die about three 



3-28 



LIUI/CIUO, J. 1>1JUI_F V 



it from the part and check the fit with the part 
that will mate with it. Make any adjustments 
necessary at this time. Replace the die on the part 
and continue threading until you reach the desired 
thread length. If you are cutting the threads to 
a shoulder, you may turn the die over and cut the 
last 2 or 3 threads with the short tapered side. 

Removing Broken Taps 

Removing a broken tap is usually a difficult 
operation and requires slow, deliberate actions to 
remove it successfully without damaging the part 
involved. There is no single method that you can 
use in all the different circumstances you may 
experience. The following information describes 
briefly some of the methods that have proven to 
be effective. You will need to evaluate the 
particular problem and attempt removal with the 
method that will work best. 

A tap that has broken and has at least 1/4 inch 
left protruding above the part can sometimes be 
grasped by locking pliers and removed. Use a 
scribe first to remove as many as of the chips as 
possible from the hole and the flutes of the tap. 
Do not use compressed air to remove the chips 
because there is always a chance that a small chip 
will be blown into either your eyes or someone's 
nearby. Apply penetrating oil around the threads 
if possible. Use a small hand grinder to shape the 
end of the tap to provide a good grip for the 
locking pliers. If they are permitted to slip on the 
tap, additional fragments will probably break 
away, giving you less surface to grasp. Apply a 
slow, even force. Excessive force or jerky 
movements will cause more damage. You may 
need to carefully rock or reverse the direction in 
which you are turning the tap in order to free it. 
This is especially true in beginning the removal. 
Use a lubricant once you have loosened the tap 
in the hole. When you have removed the tap, 
examine the hole and threads closely to ensure that 
no fragments of the tap or jagged threads remain 
to cause problems when you use another tap to 
finish or clean up the threads. 

Another method is to use a punch and apply 
sharp blows to the broken tap. You will probably 
use this method when the tap is broken below the 
surface of the part. Always wear safety goggles 
and a face shield to protect your face and eyes 
from flying fragments. Do not allow anyone to 
stand near you while you do this type of 



\Ji LJ.ll' U.j-/ ^ 1.J JTV/U Wi WtlJV U. 1 J. tig, All Will' V/i LJ.1V bU/ 

away, remove it from the hole. This method will 
probably cause serious damage to the threaded 
hole when the punch strikes the threads, or an 
oversized condition can result from forcing the 
tap around in the hole. You should be sure that 
there is an approved method of repair or 
modification of the threaded hole before under- 
taking this method of removal. 

It is sometimes possible to weld a stud to the 
top of a tap that is broken off below the surface. 
The tap diameter must be large enough for inser- 
tion of both the stud and the welding rod into the 
hole without running the risk of having the 
welding rod touch or splatter the threads. There 
are materials that can be used to help protect the 
threads. Unless you are an accomplished welder, 
do not attempt this job. Request the assistance 
of a Hull Maintenance Technician (HT). After the 
stud is welded to the tap, you can apply a more 
even pressure in removing the tap if you grind a 
square on the top of the stud so that you can use 
a tap wrench. The heat generated by the welding 
process could have expanded the tap slightly so 
that when it cooled and contracted, it may have 
loosened slightly. On the other hand, the tap may 
bind even more and the structure and condition 
of the surrounding metal may have changed. 

If the tap is broken off below the surface of 
the part, you can use a tool called a tap extractor 
(fig. 3-39) to remove it. You should try this 
method first as it does no damage to the threads. 
Tap extractors are available for each of the 
standard diameter taps over about 3/16 inch. As 
you see in figure 3-38, the tap extractor has a 
square end for using a tap wrench and sliding 
prongs or fingers that fit into each of the flutes 
on the tap. The upper collar is secured in place 
by setscrews while the bottom collar is free to 
move. Position the bottom collar as close as 



BROKEN 
/TAP 



SLIDING 
PRONG 



UPPER 
COLLAR 




SQUARE 
SHANK 



Figure 3-39. Tap extractor. 



3-29 



possible to the top of the hole to prevent the 
sliding prongs from twisting. The best results are 
obtained from this tool when the sliding prongs 
have a minimum amount of unsupported length 
exposed. Apply a slow, even pressure to the tap 
wench in removing the tap. 

In all of the methods listed, remove all chips 
prior to beginning the removal process. There are 
several methods for helping to free the tap that 
you can use with any of the removal methods if 
the particular situation lends itself to their use. 
As previously mentioned, you can apply 
penetrating oil around the threads. You can also 
apply a controlled heat to the area surrounding 
the tap to cause expansion. Be very careful to limit 
the heat so the tap does not begin to expand also. 
Since most taps are made from high-speed steel, 
this probably will not occur, but do not overlook 
the possibility. You must also consider damage 
to the part from heat. If the part is very big and 
has a large mass of metal in the immediate area, 
the heat will carry to the surrounding area rapidly, 
preventing adequate heat and expansion where it 
is needed. 

Another method, one that you must conduct 
under strict safety conditions, is to apply a 
solution of 1 part nitric acid and 5 parts water 
to the threaded hole. The nitric acid solution will 
gradually eat away some of the surface metal and 
loosen the tap. After the acid solution has worked 
for a little while, pour it out and rinse the part 
thoroughly. This method is effective primarily on 
steel parts. When you mix the acid solution add 
the acid to the premeasured amount of water. The 
procedure of adding the acid to the water is a 
safety measure because some acids react violently 
when water is added to them. You should wear 
chemically resistant goggles, a face shield, rubber 
or plastic gloves, and an apron. Nitric acid can 
damage your eyes, burn your skin, and eat holes 
in your clothes. If any acid gets on your skin, 
immediately flush the skin with water for at least 
15 minutes and seek medical attention. You will 
use nitric acid often in identifying metals. You 
should treat each occasion as seriously as the first, 
strictly observing every safety precaution. 

There is one other method for removing 
broken taps that is used primarily on tenders, 
repair ships, and shore based repair activities. It 
involves the use of a special machine (metal 
disintegrator), electrodes, and a coolant. Any 
metal that will conduct electricity can be worked 
with this machine. The action of the electrode and 
the coolant combined create a hole through the 
part that is equal in size to the diameter of the 



electrode. There are portable models available; 
however, most models either have their own 
cabinet or they are used in a drill press. Detailed 
information on this method can be found later 
in this manual. 

Classes of Fit 

The following information concerns plain 
cylindrical parts such as sleeves, bearings, pump 
wearing rings and other nonthreaded round parts 
that fit together. Fit is defined as the amount of 
tightness or looseness between two mating parts 
when certain allowances are designed into them. 
As defined earlier in this chapter, an allowance 
is the total difference between the size of a shaft 
and the hole in the part that fits over it. The 
resulting fit can be a clearance (loose) fit or 
interference (tight) fit, or a transitional 
(somewhere between loose and tight) fit. These 
three general types of fit are further divided into 
classes of fit, with each class having a different 
allowance based on the intended use or function 
of the parts involved. A brief description of each 
type fit will be given in the following paragraphs. 
Any good handbook for machinists has complete 
charts with detailed information on each class of 
fit. The majority of equipment repaired in Navy 
machine shops will have the dimensional sizes and 
allowances already specified in either the 
manufacturer's technical manual, NAVSHIPS* 
Technical Manual, or the appropriate Preventive 
Maintenance System Maintenance Requirement 
Card, which is the priority reference on 
maintenance matters. 

CLEARANCE FITS. Clearance fits, or 
running and sliding fits as they are often called, 
provide a varying degree of clearance (looseness) 
depending on which one of the nine classes is 
selected. The classes of fit range from class 1 (close 
sliding fit), which permits a clearance allowance 
of from +0.0004 to +0.0012 inch on mating parts 
with a 2.500 inch basic diameter, to class 9 (loose 
running fit), which permits a clearance allowance 
of from +0.009 to +0.0205 inch on the same parts. 
Even for a basic diameter, the small (2.500 inch) 
clearance allowance from a class 1 minimum to 
a class 9 maximum differs by +0.0201 inch. As 
the basic diameter increases, the allowance 
increases. Although the class of fit may not be 
specified on a blueprint, the dimensions given for 
the mating parts are based on the service 
performed by the parts and the specific conditions 
under which they operate. Some parts that fall 



ing rings (loose removal). 



other part. 



TRANSITIONAL FITS. Transitional fits 
are subdivided into three types known as loca- 
tional clearances, locational transition and loca- 
tional interference fits. Each of these three 
subdivisions contains different classes of fit which 
provide either a clearance or an interference 
allowance, depending on the intended use and 
class. All of the classes of fit in the transitional 
category are primarily intended for the assembly 
and disassembly of stationary parts. Stationary 
in this sense means that the parts will not rotate 
against each other although they may rotate 
together as part of a larger assembly. The 
allowances used as examples in the following 
descriptions of the various fits represent the sum 
of the tolerances of the external and internal parts. 
To achieve maximum standardization and to 
permit common size reamers and other fixed sized 
boring tools to be used as much as possible, it is 
best to use the unilateral tolerance method 
previously explained and consult one of the class 
of fit charts in a handbook for machinists. 

Locational clearance fits are broken down into 
1 1 different classes of fit. The same basic diameter 
with a class 1 fit ranges from a zero allowance 
to a clearance allowance of +0.0012 inch, while 
a class 1 1 fit ranges from a clearance allowance 
of +0.014 to +0.050 inch. The nearer a part is to 
a class 1 fit, the more accurately it can be installed 
without the use of force. 

Locational transition fits have six different 
classes providing either a small amount of clear- 
ance or an interference allowance, depending on 
the class of fit selected. The 2.500-inch basic 
diameter in a class 1 fit ranges from an interference 
allowance of -0.0003 inch to a clearance 
allowance of +0.0015 inch while a class 6 fit 
ranges from an interference allowance of 0.002 
inch to a clearance allowance of +0.0004 inch. The 
interference allowance fits may require a very light 
pressure to assemble or disassemble the parts. 

Locational interference fits are divided into 
five different classes of fit, all of which provide 
an interference allowance of varying amounts. A 
class 1 fit for a 2.500-inch basic diameter ranges 
from an interference allowance of -0.0001 to 
-0.0013 inch, while a class 5 fit ranges from an 
interference allowance of from -0.0004 to 
- 0.00023 inch. These classes of fits are used when 
parts must be located very accurately while main- 
taining alignment and rigidity. They are not 



INTERFERENCE FITS. There are five 
classes of fit within the interference type. They 
are all fits that require force to assemble or 
disassemble parts. These fits are often called force 
fits and in certain classes of fit they are referred 
to as shrink fits. Using the same basic diameter 
as an example, the class 1 fit ranges from an 
interference allowance of -0.0006 to -0.0018 
inch and a class 5 fit ranges from an interference 
allowance of - 0.0032 to - 0.0062 inch. The class 
5 fit is normally considered to be a shrink fit class 
because of the large amounts of interference 
allowance required. 

A shrink fit requires that the part with the 
external diameter be chilled or that the part with 
the internal diameter be heated. You can chill a 
part by placing it in a freezer, packing it in dry 
ice, spraying it with CO 2 (do not use a CO 2 bottle 
from a fire station) or by submerging it in liquid 
nitrogen. All of these methods except the freezer 
are potentially dangerous, especially the liquid 
nitrogen, and should NOT be used until all 
applicable safety precautions have been reviewed 
and implemented. When a part is chilled, it 
actually shrinks a certain amount depending on 
the type of material, design, chilling medium, and 
length of time of exposure to the chilling medium. 
You can heat a part by using an oxyacetylene 
torch, a heat-treating oven, electrical strip heaters 
or by submerging it in a heated liquid. As with 
chilling, all applicable safety precautions must be 
observed. When a part is heated, it expands, 
allowing easier assembly. All materials expand a 
different amount per degree of temperature 
increased. This is called the coefficient of 
expansion of a metal. Most handbooks for 
machinists include a chart of the factors and 
explain their use. It is important that you calculate 
this information to determine the maximum 
temperature increase required to expand the part 
the amount of the shrinkage allowance plus 
enough clearance to allow assembly. Overheating 
a part can cause permanent damage and produce 
so much expansion that assembly becomes 
difficult. 

A general rule of thumb for determining the 
amount of interference allowance on parts requir- 
ing a force or shrink fit is to allow approximately 
0.0015 inch per inch of diameter of the internally 
bored part. There are many variables that will 
prohibit the use of this general rule. The amount 



3-31 



of interference allowance recommended decreases 
as the diameter of the part increases. The 
dimensional difference between the inside and 
outside diameter (wall thickness) also has an 
effect on the interference allowance. A part that 
has large inside and outside diameters and a 
relatively thin wall thickness will split if installed 
with an excessive interference allowance. You 
must consider all of these variables before you 
select a fit when there are no blueprints or other 
dimensional references available. 



Hydraulic and Arbor Presses 

Hydraulic and arbor presses are used in many 
Navy machine shops. They are used to force 
broaches through parts, assemble and disassemble 
equipment with force fitted parts, and many other 
shop projects. 

Arbor presses are usually bench mounted with 
a gear and gear rack arrangement. They are used 
for light pressing jobs, such as pressing arbors or 
mandrels into a part for machining or forcing a 
small broach through a part. 

Hydraulic presses can be either vertical or 
horizontal, although the vertical design is 
probably more common and versatile. The 
pressure that a hydraulic press can generate ranges 
from about 10 to 100 tons in most of the Navy 
machine shops. The pressure can be exerted 
by either a manually operated pump or an electro- 
hydraulic pump. 

Regardless of the type of press equipment you 
use, be sure to operate it correctly. The only way 
you can determine the amount of pressure a 
hydraulic press exerts is by watching the pressure 
gauge. A part being pressed can reach the break- 
ing point without any visible indication that too 
much pressure is being applied. When using the 
press, you must consider the interference 
allowance between mating parts; corrosion and 
marred edges; and overlooked fastening devices, 
such as pins, setscrews, and retainer rings. 

To prevent damage to the work, observe the 
following precautions whenever you use a 
hydraulic press: 

Ensure that the work is adequately 
supported. 

Place the ram in contact with the work by 
hand, so that the work is positioned accurately 
in alignment with the ram. 



Use a piece of brass or other material 
(preferably slightly softer than the workpiece) 
between the face of the ram and the work to 
prevent mutilation of the "surface of the 
workpiece. 

Watch the pressure gauge. You cannot 
determine the pressure exerted by "feel." If you 
begin to apply excessive pressure, release the 
pressure and double check the work to find the 
cause. 

When pressing parts together, use a 
lubricant between the mating parts to prevent 
seizing. 

Information concerning the pressure required 
to force fit two mating parts together is available 
in most handbooks for machinists. The distance 
the parts must be pressed directly affects the 
required pressure, and increased interference 
allowance requires greater pressure. As a guideline 
for force-fitting a cylindrical shaft, the maximum 
pressure, in tons, should not exceed 7 to 10 times 
the shaft's diameter in inches. 

Oxyacetylene Equipment 

As a Machinery Repairman, you may have to 
use an oxyacetylene torch to heat parts to expand 
them enough to permit assembly or disassembly. 
Do this with great care, and only with proper 
supervision. The operation of the oxyacetylene 
torch, as used in heating parts only, is explained 
in this chapter along with safety precautions which 
you must observe when you use the torch and 
related equipment. 

Oxyacetylene equipment consists of a cylinder 
of acetylene, a cylinder of oxygen, two regulators, 
two lengths of hose with fittings, a welding torch 
with tips, and either a cutting attachment or a 
separate cutting torch. Accessories include a spark 
lighter to light the torch; an apparatus wrench to 
fit the various connections, regulators, cylinders, 
and torches; goggles with filter lenses for eye 
protection; and gloves for protection of the hands. 
Flame-resistant clothing is worn when necessary. 

Acetylene (chemical formula C 2 H 2 ) is a fuel 
gas made up of carbon and hydrogen. When 
burned with oxygen, acetylene produces a very hot 
flame having a temperature between 5700 and 
6300 F. Acetylene gas is colorless, but has a 
distinct, easily recognized odor. The acetylene 
used on board ship is usually taken from 
compressed gas cylinders. 



3-32 



burn by itself, but it will support combustion 
when combined with other gases. You must be 
extremely careful to ensure that compressed 
oxygen does not become contaminated with 
hydrogen or hydrocarbon gases or liquids, unless 
the oxygen is controlled by such means as the 
mixing chamber of a torch. A highly explosive 
mixture will be formed if uncontrolled compressed 
oxygen becomes contaminated. Oxygen should 
NEVER come in contact with oil or grease. 

The gas pressure in a cylinder must be reduced 
to a suitable working pressure before it can be 
used. This pressure reduction is accomplished by 
an LC REGULATOR or reducing valve. 
Regulators that control the flow of gas from the 
cylinder are either the single-stage or the double- 
stage type. Single-stage regulators reduce the 
pressure of the gas in one step; two-stage 
regulators do the same job in two steps, or stages. 
Less adjustment is generally necessary when two- 
stage regulators are used. 

The hose connected between the torch and the 
regulators is strong, nonporous, and sufficiently 
flexible and light to make torch movements easy. 
The hose is made to withstand high, internal 
pressures, and the rubber from which it is made 
is specially treated to remove sulfur to avoid the 
danger of spontaneous combustion. Welding hose 
is available in various sizes, depending upon the 
size of work for which it is intended. Hose used 
for light work has a 3/16- or 1/4-inch inside 
diameter, and contains one or two plies of 
fabric. For heavy duty welding and handcutting 
operations, hose with an inside diameter of 1/4 
or 5/16 inch and three to five plies of fabric is 
used. Single hose comes in lengths of 12 1/2 feet 
to 25 feet. Some manufacturers make a double 
hose which conforms to the same general 
specifications. The hoses used for acetylene and 
oxygen have the same grade but differ in color 
and have different types of threads on the hose 
fittings. The oxygen hose is GREEN and the 
acetylene hose is RED. The oxygen hose has right- 
hand threads and the acetylene hose has left-hand 
threads for added protection against switching the 
hoses during connection. 

The oxyacetylene torch is used to mix oxygen 
and acetylene gas in the proper proportions and 
to control the volume of these gases burned at the 
torch tip. Torches have two needle valves, one for 
adjusting the flow of oxygen and the other for 
adjusting the flow of acetylene. In addition, they 
have a handle (body), two tubes (one for oxygen 



which dissipates heat (less than 60% copper) and 
are available in different sizes to handle a wide 
range of plate thicknesses. 

Torch tips and mixers made by different 
manufacturers differ in design. Some makes of 
torches have an individual mixing head or mixer 
for each size of tip. Other makes have only one 
mixer for several tip sizes. Tips come in various 
types. Some are one-piece, hard copper tips. 
Others are two-piece tips that include an extension 
tube to make connection between the tip and the 
mixing head. When used with an extension tube, 
removable tips are made of hard copper, brass, 
or bronze. Tip sizes are designated by numbers, 
and each manufacturer has its own arrangement 
for classifying them. Tips have different hole 
diameters. 

No matter what type or size tip you select, you 
must keep the tip clean. Quite often the orifice 
becomes clogged. When this happens, the flame 
will not burn properly. Inspect the tip before you 
use it. If the passage is obstructed, you can clear 
it with wire tip cleaners of the proper diameter, 
or with soft copper wire. Do not clean tips with 
machinist's drills or other sharp instruments. 

Each different type of torch and tip size 
requires a specific working pressure to operate 
properly and safely. These pressures are set by 
adjusting the regular gauges to the setting 
prescribed by charts provided by the manufac- 
turer. 

PROCEDURE FOR SETTING UP OX- 
YACETYLENE EQUIPMENT. Take the 

following steps in setting up oxyacetylene 
equipment: 

1. Secure the cylinders so they cannot be 
upset. Remove the protective caps. 

2. Crack (open) the cylinder valves slightly to 
blow out any dirt that may be in the valves. Close 
the valves and wipe the connections with a clean 
cloth. 

3. Connect the acetylene pressure regulator to 
the acetylene cylinder and the oxygen pressure 
regulator to the oxygen cylinder. Using the 
appropriate wrench provided with the equipment 
tighten the connecting nuts. 

4. Connect the red hose to the acetylene 
regulator and the green hose to the oxygen 
regulator. Tighten the connecting nuts enough to 
prevent leakage. 



3-33 



5. Turn the regulator screws out until you 
feel little or no resistance then open the cylinder 
valves slowly. Then open the acetylene valve 1/4 
to 1/2 turn. This will allow an adequate flow of 
acetylene and the valve can be turned off quickly 
in an emergency. (NEVER open the acetylene 
cylinder valve more than 11/2 turns.) Open the 
oxygen cylinder valve all the way to eliminate 
leakage around the stem. (Oxygen valves are 
double seated or have diaphragms to prevent 
leakage when open.) Read the high-pressure gauge 
to check the pressure of each cylinder. 

6. Blow out the oxygen hose by turning the 
regulator screw in and then back out again. If you 
need to blow out the acetylene hose, do it ONLY 
in a well-ventilated place that is free from sparks, 
flames, or other possible sources of ignition. 

7. Connect the hoses to the torch. Connect 
the red acetylene hose to the connection gland that 
has the needle valve marked AC or ACET. 
Connect the green oxygen hose to the connection 
gland that has the needle valve marked OX. Test 
all hose connections for leaks by turning both 
regulator screws IN, while the needle valves are 
closed. Then turn the regulator screws OUT, and 
drain the hose by opening the needle valves. 

8. Adjust the tip Screw the tip into the 
mixing head and screw the mixing head onto the 
torch body. Tighten the mixing head/tip assembly 
by hand and adjust the tip to the proper angle. 
Secure this adjustment by tightening the assembly 
with the wrench provided with the torch. 

9. Adjust the working pressures Adjust the 
acetylene pressure by turning the acetylene gauge 
screw to the right. Adjust the acetylene regulator 
to the required working pressure for the particular 
tip size. (Acetylene pressure should NEVER 
exceed 15 psig.) 

10. Light and adjust the flame Open the 
acetylene needle valve on the torch and light the 
acetylene with a spark lighter. Keep your hand 
out of the way. Adjust the acetylene valve until 
the flame just leaves the tip face. Open and 
adjust the oxygen valve until you get the proper 
neutral flame. Notice that the pure acetylene flame 
which just leaves the tip face is drawn back to the 
tip face when the oxygen is turned on. 

PROCEDURE FOR ADJUSTING THE 
FLAME. A pure acetylene flame is long and 
bushy and has a yellowish color. It is burned by 
the oxygen in the air, which is not sufficient to 
burn the acetylene completely; therefore, the 
flame is smoky, producing a soot of fine, 
unburned carbon. The pure acetylene flame is 



unsuitable lor use. When the oxygen valve is 
opened, the mixed gases burn in contact with the 
tip face. The flame changes to a bluish- white color 
and forms a bright inner cone surrounded by an 
outer flame envelope. The inner cone develops the 
high temperature required. 

The type of flame commonly used for heating 
parts is a neutral flame. The neutral flame is 
produced by burning one part of oxygen with one 
part of acetylene. The bottled oxygen, together 
with the oxygen in the air, produces complete 
combustion of the acetylene. The luminous white 
cone is well-defined and there is no greenish tinge 
of acetylene at its tip, nor is there an excess of 
oxygen. A neutral flame is obtained by gradually 
opening the oxygen valve to shorten the acetylene 
flame until a clearly defined inner luminous cone 
is visible. This is the correct flame to use for many 
metals. The temperature at the tip of the inner 
cone is about 5900 F, while at the extreme end 
of the outer cone it is only about 2300 F. This 
gives you a chance to exercise some temperature 
control by moving the torch closer to or farther 
from the work. 

EXTINGUISHING THE OXYACETYLENE 
FLAME. To extinguish the oxy acetylene flame 
and to secure equipment after completing a job, 
or when work is to be interrupted temporarily, 
you should take the following steps: 

1. Close the acetylene needle valve first; this 
extinguishes the flame and prevents flashback. 
(Flashback is discussed later.) Then close the 
oxygen needle valve. 

2. Close both the oxygen and acetylene 
cylinder valves. Leave the oxygen and acetylene 
regulators open temporarily. 

3. Open the acetylene needle valve on the 
torch and allow gas in the hose to escape for 5 
to 15 seconds. Do NOT allow gas to escape into 
a small or closed compartment. Close the 
acetylene needle valve. 

4. Open the oxygen needle valve on the torch. 
Allow gas in the hose to escape for 5 to 15 
seconds. Close the valve. 

5. Close both oxygen and acetylene cylinder 
regulators by backing out the adjusting screws 
until they are loose. 

Follow the above procedure whenever your 
work will be interrupted for an indefinite period. 
If your work is to stop for only a few minutes, 
securing the cylinder valves and draining the hoses 
is not necessary. However, for any indefinite work 



in areas other than the shop, it is a good idea to 
remove the pressure regulators and the torch from 
the system and to double check the cylinder valves 
to make sure that they are closed securely. 

SAFETY: OXYACETYLENE 
EQUIPMENT 

When you are heating with oxyacetylene 
equipment, you must observe certain safety 
precautions to protect personnel and equipment 
from injury by fire or explosion. The precautions 
which follow apply specifically to oxyacetylene 
work. 

Use only approved apparatus that has been 
examined and tested for safety. 

When you use cylinders, keep them far 
enough away from the actual heating area so they 
will not be reached by the flame or sparks from 
the object being heated. 

NEVER interchange hoses, regulators, or 
other apparatus intended for oxygen with those 
intended for acetylene. 

Keep valves closed on empty cylinders. 

Do NOT stand in front of cylinder valves 
while opening them. 

When a special wrench is required to open 
a cylinder valve, leave the wrench in position on 
the valve stem while you use the cylinder so the 
valve can be closed rapidly in an emergency. 

Always open cylinder valves slowly. (Do 
NOT open the acetylene cylinder valve more than 
1 1/2 turns.) 

Close the cylinder valves before moving the 
cylinders. 

NEVER attempt to force unmatching or 
crossed threads on valve outlets, hose couplings, 
or torch valve inlets. The threads on oxygen 
regulator outlets, hose couplings, and torch valve 
inlets are right-handed; for acetylene, these 
threads are left-handed. The threads on acetylene 
cylinder valve outlets are right-handed, but have 
a pitch that is different from the pitch of the 
threads on the oxygen cylinder valve outlets. If 
the threads do not match, the connections are 
mixed. 



involved. This information should be taken from 
tables or worksheets supplied with the equipment. 

Do NOT allow acetylene and oxygen to ac- 
cumulate in confined spaces. Such a mixture is 
highly explosive. 

Keep a clear space between the cylinder 
and the work so the cylinder valves may be 
reached quickly and easily if necessary. 

When lighting the torch, use friction 
lighters, stationary pilot flames, or some other 
suitable source of ignition. The use of matches 
may cause serious hand burns. Do NOT light a 
torch from hot metal. When lighting the torch, 
open the acetylene valve first and ignite the gas 
with the oxygen valve closed. Do NOT allow 
unburned acetylene to escape into a small or 
closed compartment. 

When extinguishing the torch, close the 
acetylene valve first and then close the oxygen 
valve. 

Do NOT use lubricants that contain oil or 
grease on oxyacetylene equipment. OIL OR 
GREASE IN THE PRESENCE OF OXY- 
GEN UNDER PRESSURE WILL IGNITE 
VIOLENTLY. Consequently, oxygen must not be 
permitted to come in contact with these materials 
in any way. Do NOT handle cylinders, valves, 
regulators, hose, or any other apparatus which 
uses oxygen under pressure with oily hands or 
gloves. Do NOT permit a jet of oxygen to strike 
an oily surface or oily clothes. NOTE: A suitable 
lubricant for oxyacetylene equipment is glycerin. 

NEVER use acetylene from cylinders 
without reducing the pressure through a suitable 
pressure reducing regulator. Avoid acetylene 
working pressures in excess of 15 pounds per 
square inch. Oxygen cylinder pressure must 
likewise be reduced to a suitable low working 
pressure; high pressure may burst the hose. 

Stow all cylinders carefully according to 
prescribed procedures. Store cylinders in dry, well- 
ventilated, well-protected places away from heat 
and combustible materials. Do NOT stow oxygen 
cylinders in the same compartment with acetylene 
cylinders. Stow all cylinders in an upright 
position. If they are not stowed in an upright 
position, do not use them until they have been 
allowed to stand upright for at least 2 hours. 



3-35 



cylinder, or on any flammable materials. Be sure 
a fire watch is posted as required to prevent 
accidental fires. 

Be sure you and anyone nearby wear flame- 
proof protective clothing and shaded goggles to 
prevent serious burns to the skin or the eyes. A 
number 5 or 6 shaded lens should be sufficient 
for your heating operations. 

These precautions are by no means all the 
safety precautions that pertain to oxyacetylene 
equipment, and they only supplement those 
specified by the manufacturer. Always read the 
manufacturer's manual and adhere to all pre- 
cautions and procedures for the specific equip- 
ment you are going to be using. 

Flashback and Backfire 

A backfire and a flashback are two common 
problems encountered in using an oxyacetylene 
torch. 

Unless the system is thoroughly purged of air 
and all connections in the system are tight before 
the torch is ignited, the flame is likely to burn in- 
side the torch instead of outside the tip. The 
difference between the two terms backfire and 
flashback is this: in a backfire, there is a 
momentary burning back of the flame into the 
torch tip; in a flashback, the flame burns in or 
beyond the torch mixing chamber. A backfire is 
characteristized by a loud snap or pop as the flame 
goes out. A flashback is usually accompanied by 
a hissing or squealing sound. At the same time, 
the flame at the tip becomes smoky and sharp- 
pointed. When a flashback occurs, immediately 
shut off the torch oxygen valve, then close the 
acetylene valve. 

A flashback indicates that something is 
radically wrong either with the torch or with the 
manner of handling it. A backfire is less serious. 
Usually the flame can be relighted without 
difficulty. If backfiring continues whenever the 
torch is relighted, check for these causes; 
overheated tip, gas working pressures greater than 
that recommended for the tip size being used, 
loose tip, or dirt on the torch tip seat. These same 
difficulties may be the cause of a flashback, 
except that the difficulty is present to a greater 
degree. For example, the torch head may be 
distorted or cracked. 

In most instances, backfires and flash- 
backs result from carelessness. To avoid these 



closed) when the equipment is stowed, (3) the 
oxygen and acetylene working pressures used are 
those recommended for the torch, and (4) you 
have purged the system of air before using it. 
Purging the system of air is especially necessary 
when the hose and torch have been newly 
connected or when a new cylinder is put into the 
system. 

PURGING THE OXYACETYLENE 
TORCH. 

1 . Close the torch valves tightly, then slowly 
open the cylinder valves. 

2. Open the acetylene regulator slightly. 

3. Open the torch acetylene valve and allow 
acetylene to escape for 5 to 15 seconds, 
depending on the length of the hose. 

4. Close the acetylene valve. 

5. Repeat the procedure on the oxygen side 
of the system. 

After purging air from the system, light the 
torch as described previously. 

FASTENING DEVICES 

Parts of machinery and equipment are held 
together by several types of fastening devices. The 
fastening devices commonly used by the 
Machinery Repairman are classified into three 
general groups: threads, keys, and pins. 

The selection of the correct fastener (specified 
in blueprints, list of material blocks, and technical 
manuals) and the use of an approved installation 
method are important factors in the efficiency and 
reliability of a piece of equipment. Improper use 
of fasteners will lead to equipment failures and 
possible personnel injuries. 

Threaded Fastening Devices 

Bolts, studs, nuts, capscrews, machine screws 
and setscrews are all threaded devices used to 
clamp or secure mating parts together. Each of 
the different types has a specific range of applica- 
tions and is available in various sizes, designs and 
material specifications. The most common sizes 
evolve from the established diameters, threads per 
inch, and classes of fit described in the Unified 
(UNC, UNF) and the American National (NC, 
NF) thread systems explained in chapter 9. The 



3-36 



j. uii,v \jt. ,viivi u.j. cippjuvcii..ivji.io iv^i any givtii 

fastener. However, some equipment requires such 
specialized fasteners that the fasteners can only 
be used for that specific purpose. The material 
specification for a certain application of a fastener 
is based on the function of the mating parts, 
stresses, and temperatures applied to the 
fasteners and on the elements to which the equip- 
ment is exposed, such as steam, saltwater and oil. 
Table 3-3 is a general guide for material usage and 
the different identifying markings found on 
fasteners. 

BOLTS. A bolt is an externally threaded 
fastener, with a threaded diameter of 1/4 inch or 
larger, and either a squarely or hexagonally 
shaped head. Bolts are designed to be inserted into 
holes slightly larger than their diameter. A nut is 
attached to the threaded end to draw the mating 
parts together. As a general rule, the width of the 



thread ranges from 2 times the thread diameter 
plus 1/4 inch to a point just below the head, 
depending on the intended use. The length of the 
bolt is measured from the under side of the head 
to the tip of the threaded portion. It is best to use 
a bolt that has an unthreaded length slightly less 
than the combined thickness of the parts being 
mated. The overall length should allow a 
minimum of 1 full thread and a maximum of 10 
threads (space permitting) to protrude above the 
nut after the assembly is completely torqued 
down. The class of fit normally found on the 
threads of bolts and the nuts used with them is 
class 2A for the bolt and class 2B for the nut. 
This fit permits an allowance so that the bolt 
and nut can be assembled without seizing or 
galling. Detailed information on the different 
classes of fit for threads is covered later in this 
manual. 



Table 3-3. Specifications and Uses of Fasteners 



MATERIAL 


MATERIAL SPECS. 


GRADE 


CONDITION 


MARKING ON 
FASTENER 


INTENDED USE 


CARBON STEEL 


SAE 10XX SERIES 
STEEL WITH A MAX 
IMUM OF 0.55% 


5 


HEAT 
TREATED 


3 EQUALLY 
SPACED RADIAL 
LINES 


GENERAL USE 


CARBON STEEL 


CARBON 


8 


HEAT 
TREATED 


6 EQUALLY 
SPACED RADIAL 
LINES 


GENERAL USE 


ALLOY STEEL 


SAE 4140 TO 
SAE 4145 


B7 


HEAT 
TREATED 


B7 


FOR USE UP TO 775F WITH GRADE 2H AND 
GRADE 4 NUTS 


ALLOY STEEL 


ASTM A 193 


B16 


HEAT 
TREATED 


B16 


FOR USE UP TO 1000F WITH GRADE 4 NUT 


CORROSION 
RESISTANT STEEL 


FED. STD. 66 


303 


ANNEALED 


303 


FOR USE WHERE LOW MAGNETIC AND 
CORROSION RESISTANT PROPERTIES ARE 
REQUIRED 


CORROSION 
RESISTANT STEEL 


FED. STD. 66 


41 OT 


HEAT 
TREATED 


410 


FOR USE WHERE LOW MAGNETIC AND 
CORROSION RESISTANT PROPERTIES ARE 
REQUIRED 


NAVAL BRASS 


QQ-B-637 


482 





482 


FOR CONNECTING NON-FERROUS MATERIALS 
IN CONTACT WITH SALT WATER 


SILICON BRONZE 


QQ-C-591 


651 





651 


FOR CONNECTING NON-FERROUS MATERIALS 
IN CONTACT WITH SALT WATER 


NICKLE COPPER 


QQ-N-281 CL. A&B 


400 




400 


FOR CONNECTING FERROUS AND 
NON-FERROUS MATERIALS (EXCEPT 
ALUMINUM) IN CONTACT WITH SALT WATER 


NICKLE COPPER 

ALUMINUM 


QQ-N-286 CL.A 


500 





500 


FOR CONNECTING FERROUS AND 
NON-FERROUS MATERIALS (EXCEPT 
ALUMINUM) IN CONTACT WITH SALTWATER 


CARBON STEEL 


SAE 10XX SERIES 
STEEL WITH A 
MAX. OF 0.55% 
CARBON 


2H 


HEAT 
TREATED 


2H (NUTS ONLY) 


FOR USE UP TO 775F WITH GRADE B7 STUD OR 
BOLT 


ALLOY STEEL 


SAE 4140 to 
SAE 4145 


4 


HEAT 
TREATED 


4 (NUTS ONLY) 


FOR USE UP TO 1000F WITH GRADE B16 AND 
B7 STUD OR BOLT 



3-37 



fastener with threads on both ends. It can either 
be inserted through a clearance hole and secured 
by a nut on each end, or it can be used in an 
assembly where one part has a tapped hole and 
the second part has a clearance hole. In the latter 
case, the stud is screwed into the tapped hole and 
a nut is screwed onto the other end of the stud. 
One type of stud is continuously threaded, with 
threads beginning at one end and running the 
entire length of the stud. Another type of stud 
has threads beginning at each end and an un- 
threaded portion in the center of the stud. The 
unthreaded portion may have the same diameter 
as the major diameter of the threads, or it may 
be recessed to provide clearance. A continuously 
threaded stud generally has a class 2A or 3A fit 
to allow relative ease in assembly. A stud with the 
center portion unthreaded may have a different 
class of fit on each end. One end will have a class 
2A or 3A fit. This is the end on which the nut 
is screwed. The end of the stud that screws into 
the tapped hole will have an interference fit that 
will require a torque wrench to install it. The 
interference fit is a class 5 fit and is divided into 
several subdivisions to provide the correct fit for 
different materials and lengths of engagement. A 
stud of this type is screwed into the tapped hole 
the maximum distance possible without jamming 
either the end of the stud against the bottom of 
the hole or the shoulder of the unthreaded part 
of the stud against the top of the tapped hole. A 
small amount of lubricant approved for use in the 
temperature range in which the equipment is 
exposed should be applied to the threads. You will 
find the correct tolerances and torque required for 
each application in charts in most handbooks for 
machinists. 

NUTS. A nut is an internally threaded 
fastener with the same size threads as the 
externally threaded part to which it will be 
attached. Nuts come in either square or a hexagon 
shapes and have standard widths and thicknesses 
based on the basic thread size. Any application 
of threaded fasteners that are subjected to 
working conditions which could cause the nut to 
loosen through heat or vibration usually has some 
method of locking the mating parts securely. 
Several methods are available to you. You may 
use different styles of lock washers, deform the 
area around the threads by staking or peening with 
a center punch, install setscrews, or use locknuts. 

Locknuts in common use are of two types. 
One type applies pressure to the bolt or stud 



and is used when the nut must be removed 
frequently. Included in this type are jam nuts, a 
thin nut that goes under the regular nut; plastic 
angular ring and nylon plug insert nuts that use 
the resiliency of the plastic and nylon to create 
large frictional pressures on the bolt or stud; 
spring nuts that use springs of different types to 
apply pressure between the nut and the working 
surface; and spring beam nuts that have a slight 
taper in the upper portion of the nut with slots 
cut to form segments which permit expansion 
when the nut is screwed onto a bolt or stud. The 
other type of locknut deforms the threads on the 
bolt or stud and should be used only when 
removal is seldom required. This type includes (1) 
a distorted collar nut that has an oval shaped 
opening at the top and applies pressure when 
forced over the bolt or stud and (2) a distorted 
thread nut that has depressions in the face or 
threads of the nut. 

MACHINE SCREWS AND CAP- 
SCREWS. Machine screws and capscrews are 
similar except for size range. Machine screws have 
diameters up to 3/4 inch (including size numbers 
from to 12), while capscrews come in sizes above 
1/4-inch diameter. Both machine screws and 
capscrews are available in several head shapes, 
such as flat, fillister, and hexagonal. These 
screwheads are slotted so they can be tightened 
with a screwdriver. 

SETSCREWS. Setscrews are available in 
several different styles of heads including square, 
hexagon, slotted and the most common type, the 
recessed hexagon socket. The points on setscrews 
differ from the points on other threaded fasteners 
to permit a positive engagement with a prepared 
recess in the external surface on one of the mating 
parts. Available point shapes are a cone (90 
point), a cup (recessed point), an oval, a flat, and 
a half -dog (a short, reduced diameter). The point 
selection depends on whether the setscrew is in- 
tended to prevent slippage of a pulley or gear on 
a shaft or to hold nonrotating parts in place. 
There is a definite relationship between the 
holding power and the diameter of a setscrew and 
between the number of setscrews required to 
transmit rotational movement of equipment 
rotating at any given revolutions per minute and 
horsepower. If the equipment specifications do 
not provide this information, you may obtain it 
from most handbooks for machinists. Setscrews 
are normally made of hardened steel, although 



3-38 



corrosive liquids are involved. 
Screw Thread Inserts 

A screw thread insert (fig. 3-40) is a helically 
wound coil designed to screw into an internally 
threaded hole and receive a standard sized 
externally threaded fastener. A screw thread 
insert can be used to repair a threaded hole when 
the threads have been corroded or stripped away 
and to provide an increased level of thread 
strength when the base metal of the part is 
aluminum, zinc, or other soft materials. Before 
using screw thread inserts for a repair job, care- 
fully evaluate the feasibility of using this method. 
When you have no specific guidance, ask your 
supervisor for advice. 

Screw thread inserts come in sizes up to 
1 1/2-inch in diameter in both American National 
and Unified, coarse and fine thread series. The 
overall length of an insert is based on a fractional 
multiple of its major diameter. A 1/2-inch screw 
thread insert is available in lengths of 1/2, 3/4, 
1 inch, and so on. Screw thread inserts are 
normally made from stainless steel; however 
phosphor bronze and nickel alloy inserts are 
available by special order. A stainless steel insert 
should NOT be used in any application where the 
temperature exceeds 775 F or where a corrosive 
material such as acid or saltwater is involved. 

There are several tools associated with the 
installation and removal of screw thread inserts 
that are essential if the job is to be done correctly. 
The most important tool is the tap used to thread 
the hole that the insert will be screwed into. These 
taps are oversized by specific amounts according 
to the size of the insert, so that after installation 



pitch diameter tolerance, as previously explained 
in the section on hand taps, are marked on the 
taps. As an example of the amount of oversize 
involved, a tap required for a 1/2-13 UNC 
insert has a maximum major diameter of 0.604 
inch. Because of the increase in the size of the hole 
required, it is important to ensure that there is 
sufficient material around the hole on the part to 
provide strength. A rule of thumb is that the 
minimum amount of material around the hole 
should equal the thread size of the insert, 
measured from the center of the hole. Using this 
rule, a 1/2 - 13 UNC insert will require a 1/2-inch 
distance from the center of the hole to the nearest 
edge of the part. The tap drill size for each of the 
taps is marked on the shank of the tap. The 
diameter of this drill will sometimes vary 
according to the material being tapped. 

The next tool that you will use is an inserting 
tool (fig. 3-41). There are several styles of 
inserting tools that are designed to be used for 
a specific range of insert sizes and within each of 
these styles are tools for each individual size of 
insert. All of the inserting tools have similar 
operating charactistics. Either slip the insert over 
or screw it onto the shank of the tool until the 
tang (the horizontal strip of metal shown at the 
top of the insert in figure 3-40) solidly engages 
the shoulder or recess on the end of the tool. Then 
install the insert by turning the tool until the 
correct depth is reached. Remove the tool by 
reversing the direction of rotation. 

After you have the insert properly installed, 
break off the tang to prevent any interference with 
the fastener that will be screwed into the hole. A 
tang break-off tool is available for all insert sizes 





INSERTING TOOL 



EXTRACTOR 



Figure 3-40. Screw thread insert. 



Figure 3-41. Screw thread insert tools. 



3-39 



of 1/2 inch and below. The tang has a slight notch 
ground into it that will give way and break when 
struck with the force of the punch-type, tang 
break-off tool. On insert sizes over 1/2 inch use 
a long-nosed pair of pliers to move the tang back 
and forth until it breaks off. 

When it is necessary to remove a previously 
installed screw thread insert, use an extracting tool 
(fig. 3-41). There are several different sized tools 
that cover a given range of insert sizes; be sure 
you select the correctly sized tool. Insert the tool 
into the hole so the blade contacts the top coil of 
the insert approximately 90 from the beginning 
of the insert coil. Then, lightly hit the tool to cause 
the blade to cut into the coil. Turn the tool 
counterclockwise until the insert is clear. 

The steps involved in repairing a damaged 
threaded hole with a screw thread insert are as 
follows: 

1. Determine the original threaded hole size. 
Select the correct standard sized screw thread 
insert with the length that best fits the applica- 
tion. Be sure the metal from which the insert is 
made is recommended for the particular 
application. 



2. Select the correct tap for the insert to be 
installed. Some taps come in sets of a roughing 
and a finishing tap. 

3 . Select the correct size of drill based on the 
information on the shank of the tap or from 
charts normally supplied with the insert kits. 
Measure the part with a rule to determine if the 
previously referenced minimum distance from the 
hole to the edge of the part exists. With all 
involved tools and parts secured rigidly in place, 
drill the hole to a minimum depth that will permit 
full threads to be tapped a distance equaling or 
exceeding the length of the insert, not counting 
any spot-faced or countersunk area at the top of 
the hole. Remove all chips from the hole. 

4. Tap the hole. Use standard tapping 
procedures in this step. If the tapping procedure 
calls for both roughing and finishing taps, be sure 
to use both taps prior to attempting to install the 
insert. Use lubricants to improve the quality of 
the threads. When you have completed the 
tapping, inspect the threads to ensure that full 
threads have been cut to the required depth of the 
hole. Remove all chips. 

5. Next, install the insert. If the hole being 
repaired is corroded badly, apply a small amount 
of preservative, such as zinc chromate, to the 




'T 

H 



D 




FLAT BOTTOM 
OPTIONAL 







V V 



A. SQUARE 



B. RECTANGULAR 



C. WOODRUFF 



Figure 3-42. Types of keys and keyseats. 



required by the particular style being used. Turn 
the tool clockwise to install the insert. Continue 
to turn the tool until the insert is approximately 
1/2 turn below the surface of the part. Remove 
the tool by turning it counterclockwise. 

6. Use an approved antiseize compound when 
screwing the threaded bolt or stud into the insert. 
Avoid using similar metals such as a stainless 
insert and a stainless bolt to prevent galling and 
seizing of the threads. 

Keyseats and Keys 

Keyseats are grooves cut along the axis of the 
cylindrical surface of a shaft and the bored hole 
in a hub. Metal keys of various shapes are fitted 
into these grooves to transfer torque between the 
shaft and the hub. There are basically three types 
of keys: taper, parallel and Woodruff. The 
standard taper keys have a taper of 1/8 inch per 
foot and are either a plain taper or a gib head 
taper style key. Taper keys are not often found 
on marine equipment and will not be covered in 
this text. Parallel keys consist mainly of square 
and rectangular shaped keys. These are probably 
the most common types of keys that you will work 
with. A Woodruff key is a semicircular shaped 
key designed primarily to permit easy removal of 
pulleys from shafts. Keys are made from several 
different types of metal including medium carbon 
steel, nickel steel, nickel-copper alloy, stainless 
steel and several bronze alloys. Each different key 
style and material has a particular use for which 
it is best suited, depending on the forces and 



when replacing a key to prevent selecting one that 
will not perform as required. 

Square keys (fig. 3-42A) are recommended for 
applications where the shaft diameter is 6 1/2 
inches and below, while rectangular keys (fig. 
3-42B) are recommended for shaft diameters over 
6 1/2 inches. Some applications may require that 
two keys be installed to drive equipment under 
high torque conditions. The width and height of 
a key depend on the diameter of the shaft that 
it will be used on, while the length of the key is 
based on the key's width. A chart giving some 
of the more common sizes of shafts and 
recommended key size combinations is provided 
in table 3-4. 

Parallel keys (square and rectangular) and the 
keyseats machined to accept them are designed 
to provide assembly fits of three different classes. 
Each of the classes gives the recommended 
tolerance on both the key and the keyseat for the 
fit on the sides and the top and bottom of the 
keyed assembly. The top and bottom tolerances 
for the key and keyseat assemblies generally 
provide a range of fit from metal-to-metal up to 
approximately 0.040-inch clearance (depending on 
the width of the key) for all three classes of fits. 
The side fit for a class 1 fit allows for a metal to 
metal 0.017-inch clearance fit. The amount of 
clearance increases as the width of the key 
increases. A class 2 fit allows for a side fit 
ranging from a 0.002-inch clearance to an 
interference fit of up to 0.003 inch. A class 3 fit 
allows only an interference fit for the sides of the 
key with individual applications determining the 



Table 3-4. Key Size Versus Shaft Diameter. 



SHAFT DIAMETER 


KEY SIZE KEY LENGTH "L" 






WIDTH "W" 


HEIGHT "H" 


MIN. 


MAX. 


FROM 


TO 




SQUARE 


RECTANGULAR 


4XW 


16XW 


7/8" 


1 1/4" 


1/4" 


1/4" 


3/16" 


1" 


4' 


1 1/4" 


1 3/8" 


5/16" 


5/16" 


1/4" 


1 1/4" 


5' 


1 3/8" 


1 3/4" 


3/8" 


3/8" 


1/4" 


1 1/2" 


6' 


1 3/4" 


2 1/4" 


1/2" 


1/2" 


3/8" 


2" 


8' 


4 1/2" 


5 1/2" 


1 1/4" 


1 1/4" 


7/8" 


5" 


20' 


6 1/2" 


7 1/2" 


1 3/4" 


1 3/4" 


1 1/2" 


7" 


28' 



Selective excerts extracted from "American 
Society of Mechanical Engineers" USAS 
B 17. 1-1 967 Page 2, table 1 



3-41 



shaft diameters and the allowable tolerance for 
each of the classes of fit are available in most 
handbooks for machinists. 

The ends of square or rectangular keys are 
often prepared with a radius equal to one-half of 
the width as shown in the top illustration of figure 
3-42B. This design permits a snug assembly fit 
when the machining on the keyseat was done with 
a conventional milling machine and an end mill 
cutter. 

Woodruff keys (fig. 3-42C) are manufactured 
in various diameters and thicknesses. The circular 
side of the key is seated in a keyseat milled in the 
shaft with a cutter having the same radius and 
thickness as the key. 

The size of a Woodruff key is designated by 
a system of numbers which represent the nominal 
key dimensions. The last two digits of the number 
indicate the diameter of the key in eighths of an 
inch, while the digit or digits preceding them 
indicate the width of the key in thirty-seconds of 
an inch. Thus, a number 404 key would be 4/8 
or 1/2 inch in diameter and 4/32 or 1/8 inch wide, 
while a number 1012 key would be 12/8 or 1 1/2 
inches in diameter and 10/32 or 5/16 inch wide. 

For proper assembly of keyed members, 
clearance is required between the top surface of 
the key and the key seat. This clearance is 
normally approximately 0.006 inch. 

Positive fitting of the key in the keyseat is 
provided by making the key 0.0005 to 0.001 inch 
wider than the seat. 

Information on the machining of keyseats for 
parallel and Woodruff keys is included in chapter 
11. 

Pins 

The three pins commonly used in the machine 
shop are the dowel pin, the taper pin, and the 
cotter pin. The DOWEL PIN, which is made of 
machine-finished round stock, is used for aligning 
parts. It is used in applications such as pump 
housings. A hole in the housing matches with a 
hole in the end casing and a dowel pin is inserted 
to provide exact alignment. As this is an aligning 
pin, the dowel must have a light drive fit. The 
TAPER PIN which has a 1/4-inch per foot taper 
is used to hold slow-speed, low-torque, rotor-shaft 
applications, such as hand-operated wheels and 
levers on machine tools. When taper pins are 
used, the hole must be drilled and then reamed 
with a taper pin reamer to obtain the correct 



1 \J L4.lJ.vl XXJ.V L>dJ. J L v v*l\. W 11J.W11 CtJL W L-ltJ V'H L/A J.HJlW-1 JLJL V LU 

lock nuts in place on bolts. All pins come in a 
variety of standard sizes and lengths. Most 
machinist's handbooks give information on hole 
sizes and numbers for specific dimensions of pins. 

Gaskets, Packing and Seals 

Many of the repair jobs that you do will 
require the installation of gaskets, packing, or 
seals to prevent leakage. Gaskets are used mainly 
for sealing fixed type joints such as flanged pipe 
and valve joints and pump casings, while packing 
and seals are used for sealing joints where one part 
moves in relation to the other. All of these seal- 
ing devices are available in a wide range of 
diameters, thicknesses and classifications (grades) 
to provide suitable sealing of any system or 
equipment. A general knowledge of the different 
sealing materials is important; however, the 
proper selection of a gasket, packing or other seal 
must never be based on general application 
guidelines or memory. The modern ships of to- 
day have systems that reach 1000F in 
temperature and 2050 psi in pressure under nor- 
mal operating conditions. A wrong selection can 
cause serious injury to personnel and major 
damage to equipment. The equipment's technical 
manual, allowance parts list, snip's plan on the 
appropriate PMS Maintenance Requirement Card 
are sources that can provide the exact specifica- 
tions required for the sealing device. 

A brief description of some of the more 
common types of gaskets, packing, and seals used 
in shipboard equipment and their general applica- 
tion is provided in the following paragraphs. 

Gaskets 

Spiral wound, metallic-asbestos gaskets are 
composed of alternate layers of dovetailed 
stainless steel ribbon and strips of asbestos spirally 
wound, ply upon ply, to the desired diameter. The 
gasket is then placed in a solid steel retainer ring 
to keep the gasket material intact, to assist in 
centering the gasket on the flange, and to act as 
a reinforcement to prevent blowouts. This type 
gasket is used on steam, boiler feedwater, fuel and 
lubricating oil systems. System pressures of 100 
to 2050 psi and normal operating temperatures 
of 1 50 of 1000 F are within the range that these 
gaskets can effectively seal. Each application 
requires a specific gasket and substitutions should 
not be considered. When installing this gasket, 



3-42 



thickness required for the particular application. 

Synthetic rubber and cloth inserted rubber 
gaskets are used on freshwater and seawater 
systems with pressures of 50 to 400 psi and 
temperatures of 150 to 250 F. 

Gasoline and JP-5 systems require a gasket 
made from Buna-N and cork. The use of the 
wrong gasket material in these systems will result 
in a deterioration of the gasket resulting in 
contamination of the system and a hazardous 
situation if a leak should develop. 

Prior to installing any gasket, carefully inspect 
the surfaces of the mating parts for cuts or 
scratches that will prevent the proper sealing of 
the gasket. When any doubt exists, refinish the 
surface. You will find additional information on 
flange refinishing later in this manual. 

Packing 

The packing used to seal against leakage 
around equipment, such as valve stems on pump 
shafts, is available in many different material 
types, shapes, and sizes. Specific recommenda- 
tions on packing selection is best left to the 
appropriate technical document; however, there 
are some common errors made in packing 
selection and installation that are important to 
note. Packing that has a metallic or semimetallic 
base should not be used on a brass or bronze part. 
Parts that are softer than 250 BRINELL hard- 
ness should not be packed with a copper bearing 
packing. The surface condition of the valve stem 
or shaft and the stuffing box into which the pack- 
ing is placed are important also. A surface that 
has pits and scratches which could provide a path 
for leakage should be repaired. An out-of-round 
condition will cause excessive clearance between 
the packing and the rotating part. A type of pack- 
ing called corrugated ribbon packing, which is 
intended for steam valves, requires very close 
control over the finishes, dimensions, and 
concentricity of the parts that contact it. Each part 
must be measured and checked carefully before 
this type packing can be used. 

Seals 

The types of seals you will work with most 
often are oil seals, mechanical seals, and O-rings. 
Each type requires careful attention to the 
contact area and the installation procedures to 
ensure a good seal against leakage. 



cup or flange retainer, which press fits into a 
cylindrical bore, and a spring-loaded rubber or 
neoprene lip, which make contact with the shaft. 
The spring will cause the seal to maintain a firm 
contact with the shaft even if there is a small 
amount of shaft runout. The seal contact area on 
the shaft must be free of pits, scratches and old 
wear patterns to operate as designed. When 
replacing a seal of this type, be particularly careful 
in selecting the proper seal as indicated by the 
equipment manufacturer. The type of fluid 
being sealed and the operating temperature are 
as important in correct seal selection as the 
dimensions of the seal. 

Mechanical seals are considerably more 
difficult to install correctly. The majority of 
mechanical seals consist of one part that is sealed 
against the housing or seal retainer with a gasket 
or O-ring, while another part of the seal is 
attached to the shaft and is sealed by a rubber or 
neoprene bellows. Each of these two parts has a 
flat-faced seal that makes a rubbing contact when 
the shaft is turning. One of the flat-faced seals 
is spring-loaded to maintain a constant contact 
pressure when end play occurs in the equipment 
during operation. The flat-faced seals may be 
made from carbon, alloy steel, ceramic, or several 
other materials. Regardless of the material used 
for these parts, they should be handled very 
carefully to avoid damage. The installation 
instructions provided by the seal or equipment 
manufacturer should be followed very closely to 
ensure the correct loading and proper function- 
ing of the seal. Shaft runout, alignment, and end 
play (thrust) must be within the limitations 
prescribed for the equipment. 

O-rings may be used as a static seal where no 
motion exists between the mating parts or as a 
dynamic seal where a reciprocating, oscillating, 
or rotary motion exists between the mating parts. 
O-rings are made from either synthetic or natural 
materials which have the capability of returning 
to their original shape and size after being 
deformed. The substance being sealed and the 
operating pressures and temperatures are very 
important factors in determining the exact O-ring 
to use in any given application. Preparation of 
the O-ring groove requires special care to ensure 
that the specified finish and dimensions are 
obtained. The annular or circular finish pattern 
(lay) produced by a lathe provides a surface that 
allows a more effective seal than one produced 
by an end mill cutter in a milling machine. 



3-43 



A roughness value of 32 microinches for a static 
seal and 15 microinches for a dynamic seal is 
generally acceptable for the O-ring groove. To 
achieve maximum effectiveness, an O-ring should 
not be stretched more than 5% beyond the 
designed dimension of the inside diameter after 
the O-ring is in position in the groove. This can 
be controlled only by accurate machining and 
measuring of the depth of the O-ring groove. 
Excessive width of the groove will allow the 
O-ring to roll or twist during installation and 
operation. Many applications require the use of 



backup rings which are placed on one or 
both sides of the O-ring to provide additional 
protection against O-ring distortion under 
pressure. The equipment specifications should 
be reviewed carefully to determine if a backup 
ring is required. An approved O-ring lubricant 
is essential during installation to prevent 
damage to the O-ring and to enhance the 
sealing effectiveness. The lubricant selected 
should be one that will not affect the O-ring 
material or contaminate the substance being 
sealed. 



civ * 



METALS AND PLASTICS 



A Machinery Repairman is expected to repair 
broken parts and to manufacture replacements 
according to samples and blueprints. To choose 
the metals and plastics best suited for fabrication 
of replacement parts, you must have a knowledge 
of the physical and mechanical properties of 
materials and know the methods of identifying 
materials that are not clearly marked. For 
instance, stainless steel and nickel-copper are quite 
similar in appearance, but completely different 
in their mechanical properties and cannot be 
used interchangeably. A thermosetting plastic 
may look like a thermoplastic but the former 
is heat resistant, whereas the latter is highly 
flammable. Some of the properties of materials 
that an MRS and MR2 must know are presented 
in this chapter. 



PROPERTIES OF METALS 

The physical properties of a metal determine 
its behavior under stress, heat, and exposure 
to chemically active substances. In practical 
application, the behavior of a metal under 
these conditions determines its mechanical 
properties; indentation and rusting. The 
mechanical properties of a metal, therefore, are 
important considerations in selecting material for 
a specific job. 



STRESS 

Stress in a metal is its internal resistance to 
a change in shape (deformation) when an external 
load or force is applied to it. There are three 
different forms of stress to which a metal may 
be subjected. Tensile stress is a force that pulls 
a metal apart. Compression stress is a force that 
squeezes the metal. Shear stress is forces from 
opposite directions that work to separate the 
metal. When a piece of metal is bent, both tensile 



and compression stresses are applied. The side of 
the metal on the outside of the bend undergoes 
tensile stress as it is stretched, while the 
metal on the inside of the bend is squeezed under 
compression stress. When a metal is subjected to 
a torsional load such as a sump shaft driven by 
an electric motor, all three forms of stress are 
applied to a certain degree. 



STRAIN 

Strain is the deformation or change in shape 
of a metal that results when a stress or load is 
applied. When the load is removed, the metal is 
no longer under a strain. The type of deforma- 
tions which result when a metal is subjected to 
a stress will be similar to the form of stress 
applied. 



STRENGTH 

Strength is the property of a metal which 
enables it to resist strain (deformation) when a 
stress (load) is applied. The strength of a metal 
may be expressed by several different terms. The 
most commonly used term is tensile strength. 
Tensile strength is the maximum force required 
to pull metal apart. To find the tensile strength 
of a metal, divide the force required to pull the 
metal apart by the area in square inches of a 
prepared specimen. 

Another term used often to describe the 
strength of a metal is yield strength. The yield 
strength is determined during the same test that 
establishes the tensile strength. The yield strength 
is established when the metal specimen first begins 
to elongate (stretch) while pressure is gradually 
applied. A relationship between the tensile 
strength and the hardness of metals is often 
present. As the hardness of a metal is increased, 
the tensile strength is also increased and vice versa. 



4-1 



LUC muic cuuuj.nju.iy uacu 

Some other terms that may be used to describe 
a metal's strength are compression strength, shear 
strength, and torsional strength. You will not see 
these terms often. However, in certain design 
applications, where stress would result in strains 
of one of these types being applied to a part, you 
would need to establish and use specific values 
in safety computations. 



PLASTICITY 

Plasticity is the ability of a metal to withstand 
extensive permanent deformation without break- 
ing or rupturing. Modeling clay is an example of 
a highly plastic material, since it can be deformed 
extensively and permanently without rupturing. 
Metals with a high plasticity value will produce 
long, continuous chips when machined on a lathe. 



ELASTICITY 

Elasticity is the ability of a metal to return to 
its original size and shape after an applied force 
has been removed. Steel used to make springs is 
an example of applying this property. 



DUCTILITY 

Ductility is the ability of a metal to be 
permanently deformed by bending or by being 
stretched into wire form without breaking. To 
find the ductility of a metal, measure the 
percentage of elongation which results when the 
metal is stretched during the tensile strength test. 
Copper is an example of a very ductile metal. 



MALLEABILITY 

Malleability is the ability of a metal to be 
permanently deformed by a compression stress 
produced by hammering, stamping, or rolling the 
metal into thin sheets. Lead is a highly malleable 
metal. 



BRITTLENESS 

Brittleness is the tendency of a metal to break 
or crack with no prior deformation. Generally, 



brittle metals. 



TOUGHNESS 

Toughness is the quality that enables a 
material to withstand shock, to endure stresses 
and to be deformed without breaking. A tough 
material is not easily separated or cut and can be 
bent first in one direction and then in the opposite 
without fracturing. 



HARDNESS 

Hardness of a metal is generally defined as its 
ability to resist indentation, abrasion or wear, and 
cutting. The degree of hardness of many metals 
may be either increased or decreased by being 
subjected to one or more heat treatment processes. 
In most cases, as the hardness of a steel is 
decreased, its toughness is increased. 



HARDENABILITY 

Hardenability is a measure of the depth 
(from the metal's surface toward its center) 
that a metal can be hardened by heat treatment. 
A metal that achieves a shallow depth of hard- 
ness and retains a relatively soft and tough core 
has a low hardenability value. The hardenability 
of some metals can be changed by the addition 
of certain alloys during the manufacturing 
process. 



FATIGUE 

Fatigue is the action which takes place in a 
metal after a repetition of stress. When a sample 
is broken in a tensile machine, a definite load is 
required to cause that fracture; however, the same 
material will fail under a much smaller load if the 
load is applied and removed many times. In this 
way, a shaft may break after months of use even 
though the load has not been changed. The pieces 
of such a part will not show any sign of 
deformation; but the mating areas of the section 
that fractured last will usually be quite coarse 
grained, while the mating areas of other sections 
of the break will show signs of having rubbed 
together for quite some time. 



4-2 



highly resistant to practically all types of corrosive 
agents, others to some types of corrosive agents, 
and still others to only a very few types of 
corrosive substances. Some metals, however, can 
be made less susceptible to corrosive agents by 
either coating or alloying them with other metals 
that are corrosion resistant. 



HEAT RESISTANCE 

Heat resistance is the property of a steel 
or alloy that permits the steel or alloy to 
retain its properties at elevated temperatures. 
For example; red hardness in tungsten steel; high 
strength for chromium molybdenum steel; 
nondeforming qualities for austenitic stainless 
steel; malleability for forging steels. Tungsten steel 
(which even when red hot can be used to cut other 
metals) and chromium molybdenum steel (which 
is used for piping and valves in high temperature, 
high-pressure steam systems) are examples of heat 
resistant metals. 



WELDABILITY 

Weldability refers to the relative ease with 
which a metal can be welded. The weldability of 
a metal part depends on many different factors. 
The basic factor is the chemical composition of 
the elements that were added during the metal's 
manufacture. A steel with a low carbon content 
will be much easier to weld than a metal with a 
high carbon content. A low alloy steel that has 
a low hardenability value will lend itself more 
readily to welding than one with a high 
hardenability value. The welding procedure, 
such as gas or arc welding, also must be 
considered. The design of the part, its thickness, 
surface condition, prior heat treatments, and 
the method of fabrication of the metal also 
affect the weldability. Charts are available 
that provide guidelines concerning the weldability 
of a metal and the recommended welding 
procedure. The weldability of a metal should be 
considered an integral part of planning a job that 
requires the manufacture or repair of equipment 
components if any metal buildup or weld joint 
is involved. 



IU.I.IA V/J. 



used in machine shops. The machinability of each 
metal is given as a percentage of 100, with Bl 1 12, 
a resulphurized, free-machining steel, used as a 
basis for comparison. The higher rated metals can 
be cut using a higher cutting speed or surface feet 
per minute than those with lower ratings. 

There are several factors that affect the 
machinability of a metal: a variation in the 
amount or type of alloying element, the method 
used by the manufacturer to form the metal bar 
(physical condition), any heat treatment which has 
changed the hardness, the type of cutting tool used 
(high-speed steel or carbide) and whether or not 
a cutting fluid is used. Information concerning 
some of these factors will be discussed later in this 
chapter and in chapter 8. Details of the AISI and 
SAE designations used in the chart are explained 
later in this chapter. 



METALS 

Metals are divided into two general types 
ferrous and nonferrous. Ferrous metals are those 
whose major element is iron. Iron is the basis for 
all steels. Nonferrous metals are those whose 
major element is not iron, but they may contain 
a small amount of iron as an impurity. 



FERROUS METALS 

Iron ore, the basis of all ferrous metals, is 
converted to metal (pig iron) in a blast furnace. 
Alloying elements can be added later to the pig 
iron to obtain a wide variety of metals with 
different characteristics. The characteristics of 
metal can be further changed and improved by 
heat treatment and by hot or cold working. 



Pig Iron 

The product of the blast furnace is called pig 
iron. In early smelting practice, the arrangement 
of the sand molds into which the molten crude 
iron was drawn resembled groups of nursing pigs, 
hence the name. 



4-3 



Table 4-1. Machinability Rating 



SAE-AISI BHN Machinability 
Numbers % 

Plain Carbon Steels 



SAE-AISI 
Numbers 



BHN 



B-1006 147 


78 


B-1010 147 


78 


C-1008 175 


66 


C-1010 172 


65 


C-1015 160 


72 


C-1016 148 


78 


C-1017 163 


72 


C-1019 146 


78 


C-1020 162 


72 


C-1022 147 


78 


C-1023 154 


75 


C-1025 162 


72 


C-1030 164 


70 


C-1035 162 


70 


C-1040 179 


64 


C-1043 178 


64 


C-1045 199 


60 


C-1046 203 


57 


C-1050 210 


55 


C-1054 217 


53 


C-1055 221 


52 


C-1059 222 


52 


C-1060 223 


51 


C-1064 224 


50 


C-1065 229 


50 


C-1069 231 


48 


C-1070 230 


49 


C-1075 238 


48 


C-1080 271 


42 


C-1085 269 


42 


C-1090 273 


42 


C-1095 274 


42 


Resulphurlzed Carbon Steels 


Bessemer FCC 




C-1106 150 


79 


C-1108 149 


80 


C-1109 152 


81 


C-1110 148 


83 


B-llll 131 


94 


B-1112 122 


100 


B-1113 101 


132 


C-1113 120 


100 


C-1115 150 


81 


C-1116 139 


94 


C-1118 139 


91 


C-1119 120 


100 


C-1125 152 


81 


C-1126 150 


81 


C-1137 169 


72 


C-1138 164 


75 


C-1140 171 


72 


C-1146 167 


76 


C-1151 180 


70 


Manganese Steels 




Mn 1.75% 




1320 210 


57 


1321 212 


59 


NE 1330 210 


60 


1335 211 


60 


NE 1340 216 


57 


Nickel Steels 




NI 3.50% 




2317 185 


66 


2330 220 


55 


2335 242 


51 


2340 210 


57 


2345 231 


51 



Nickel Steels 
NI 5. 00* 

2512 210 

2515 212 

NE 2517 215 



Machinability 

% 



SAE-AISI BHN Machinability 
Numbers % 



Nickel -Chrome Steels 

NI 1.25* 

Cr 0.655! or 0.80* 



3115 
3120 
3130 
3135 
3140 
3145 
3150 



191 
190 
213 
225 
282 
192 
201 



66 
66 
57 
53 
44 
64 
60 



Nickel -Chrome Steels 
NI 3. SOX Cr 1.55% 



E 3310 
E 3316 



241 
250 



Molybdenum Steels 
Mo 0.25% 



4017 
4023 
4024 
4027 
4028 
4032 
4037 
4042 
4047 
4053 
4063 



185 
182 
182 
212 
191 
184 
189 
198 
204 
261 
153 



Chrome-Moly Steels 
Cr 0.95% Mo 0.20% 



4130 
E 4132 
4135 
4137 
E 4137 
4140 
4142 
4145 
4147 
4150 



181 
190 
189 
209 
205 
212 
227 
221 
219 
242 



78 
78 
78 
66 
72 
76 
73 
70 
65 
53 
52 



72 
72 
70 
65 
67 
62 
59 
60 
60 
59 



Nickel -Chrome-Moly Steels 
NI 1.80% Cr 0.50% Mo 0.25% 



4317 


215 


60 


4320 


201 


63 


E 4337 


243 


54 


4340 


240 


57 


E 4340 


239 


57 


Nickel -Moly 


Steels 




NI 1.80% Mo 


0.25% 




4608 


242 


58 


E 4617 


201 


66 


4615 


192 


66 


4620 


198 


64 


X 4620 


193 


66 


E 4620 


202 


64 


4621 


199 


66 


4640 


198 


66 


E 4640 


245 


51 



Nickel -Moly Steels 
NI '3.50% Mo 0.25% 




4812 249 
4815 256 
4817 251 
4820 248 


51 
51 
51 
53 


Chrome Steels 
Cr 0.30% or 0.60% 




5045 188 
5046 186 


70 
70 



Chrome Steels 

Cr 0.80%, 0.95% or 1.05% 



5120 
5130 
5132 
5135 
5140 
5145 
5147 
5150 
5152 



187 
241 
189 
188 
192 
210 
211 
215 
216 



75 
57 
72 
72 
70 
65 
66 
64 
64 



Carbon-Chrome Steels 

C 1.00% 

Cr 0.50%, 1.00% or 1.45% 



E 50100 211 
E 51100 221 
E 52100 220 



45 
40 
40 



Chrome-Vanadium Steels 
Cr 0.85% or 0.95% 
V 0.10% or 0.15% 



6102 
6145 
6150 
6152 



202 
182 
192 
195 



57 
66 
60 
60 



Nickel -Chrome-Moly Steels 
N1 0.55% Cr 0.50% Mo 0.20% 



8617 


182 


66 


8620 


183 


66 


8622 


185 


65 


8625 


189 


62 


8627 


188 


64 


8630 


161 


72 


8635 


165 


70 


8637 


164 


70 


8640 


172 


66 


8642 


177 


65 


8645 


182 


64 


8647 


194 


60 


8650 


195 


60 


8653 


203 


56 


8655 


205 


57 


8660 


215 


54 



Nickel -Chrome-Moly Steels 
NI 0.55% Cr 0.50% Mo 0.259% 



8719 
8720 
8735 
8740 
8742 
8747 
8750 



175 
178 
171 
183 
185 
192 
194 



67 
66 
70 
66 
64 
60 
60 



Manganese-Silicon Steels 
Mn 0.55% SI 2.00% 



9255 
9260 
9262 



122 
238 
235 



54 
51 
49 



SAE-AISI BHN Machinability 
Numbers % 

Nickel -Chrome-Moly Steels 
N1 3.25% Cr 1.20* Mo 0.12* 



E 9310 
E 9315 
E9317 



243 
238 
239 



48 
50 
49 



Manganese-Nickel -Chrome-Moly 

Steels 

Mn 1.00* N1 0.45* 

Cr 0.40% Mo 0.12* 



9437 
9440 
9442 
9445 



182 
183 
179 
181 



66 
66 
66 
64 



Nickel -Chrome-Moly Steels 
N1 0.55* Cr 0.17% Mo 0.20* 



9747 
9763 



187 
215 



64 
54 



Nickel -Chrome-Moly Steels 
N1 1.00* Cr 0.80% Mo 0.25* 



9840 
9845 
9850 



232 
238 
242 



Stainless Steels 

302 

303* 

304 

308+ 

309+ 

314+ 

317+ 

321 

330* 

347 

403 

410 

416* 

420 

420 F* 

430 

430 F** 

440 

440 A 

440 B 

440 C 

440 F* 



50 
49 
45 



45 
60 
45 
27 
28 
32 
29 
36 
27 
36 
39 
54 
72 
57 
79 
54 
91 
37 
45 
42 
40 
59 



+ Poorest Machining Properties. 
* Fairly Good Machlnlng-Contaln 

Sulfur and Selenium.' 
** Best Machining Properties. 

Cast Iron 



Soft 130 
Medium 168 
Hard 243 


81 
64 

47 


Malleable Iron 




Malleable 
Iron 115 
Malleable 
Iron 135 


106 
80 


Cast Steel 




Cast Steel 121 
Cast Steel 219 
Cast Steel 245 


85 
50 
44 



amounts of impurities, is seldom used directly as 
an industrial manufacturing material. It is, 
however, used as the basic ingredient in making 
cast iron, wrought iron, and steel. 

Cast Iron 

Cast iron is produced by resmelting a charge 
of pig iron and scrap iron in a furnace and 
removing some of the impurities from the molten 
metal by using various fluxing agents. There are 
many grades of cast iron, based on strength and 
hardness. The quality depends upon the extent of 
refining, the amount of scrap iron used, and the 
method of casting and cooling the molten metal 
when it is drawn from the furnace. The higher 
the proportion of scrap iron, the lower the grade 
of cast iron. Cast iron has some degree of 
corrosion resistance and great compressive 
strength, but at best is brittle and has a 
comparatively low tensile strength. Therefore, it 
has very limited use in marine service. 

Wrought Iron 

Wrought iron is a highly refined pure iron 
which has uniformly distributed particles of slag 
in its composition. Wrought iron is considerably 
softer than cast iron and has a fibrous internal 
structure, created by the rolling and squeezing 
given to it when it is being made. Like cast iron, 
wrought iron is fairly resistant to corrosion and 
fatigue. Wrought iron, because of these 
characteristics, is used extensively for low-pressure 
pipe, rivets, and nails. 

Plain Carbon Steels 

Pig iron is converted into steel by a process 
which separates and removes impurities from the 
molten iron by use of various catalytic agents and 
extremely high temperatures. During the refining 
process, practically all of the carbon originally 
present in the pig iron is burned out. In the final 
stages when higher carbon alloys are desired, 
measured amounts of carbon are added to the 
relatively pure liquid iron to produce carbon steel 
of a desired grade. The amount of carbon added 
controls the mechanical properties of the finished 
steel to a large extent, as will be pointed out in 
succeeding paragraphs. After the steel has been 
drawn from the furnace and allowed to solidify, 
it may be sent either to the stockpile or to shaping 



Plain steels that have small additions of sulfur 
(and sometimes phosphorous) are called free 
cutting steels. These steels have good machining 
characteristics and are used in applications similar 
to carbon steels. The addition of sulfur and 
phosphorous limits their ability to be formed hot. 

LOW CARBON STEEL (0.05% TO 0.30% 
carbon), usually referred to as mild steel, can be 
easily cut and bent and does not have great tensile 
strength, as compared with other steels. Low 
carbon steels which have less than 0.15% carbon 
are usually more difficult to machine than steel 
with a higher carbon content. 

MEDIUM CARBON STEEL (0.30% TO 
0.60% carbon) is considerably stronger than low 
carbon steel. Heat treated machinery parts are 
made of this steel. 

HIGH CARBON STEEL (0.60% to 1.50% 
carbon) is used for many machine parts, hand- 
tools, and cutting tools, and is usually referred 
to as carbon tool steel. Cutting tools of high 
carbon steel should not be used when the cutting 
temperature will exceed 400 F. 

Alloy Steels 

The steels discussed thus far are true alloys of 
iron and carbon. When other elements are added 
to iron during the refining process, the resulting 
metal is called alloy steel. There are many types, 
classes, and grades of alloy steel. 

Alloy steels usually contain several different 
alloying elements, with each one contributing a 
different characteristic to the metal. Alloying 
elements can change the machinability, har den- 
ability, weldability, corrosion resistance and the 
surface appearance of the metal. Knowledge of 
how each of the alloying elements affects a metal 
will allow you to more readily select the best metal 
for a given application and then to determine 
which, if any, heat treatment process should be 
used to achieve the best mechanical properties. 
A few of the more common alloy steels and the 
effects of certain alloying elements upon the 
mechanical properties of steel are discussed briefly 
in the following paragraphs. 

CHROMIUM. Chromium is added to steel 
to increase hardenability, corrosion resistance, 
toughness, and wear resistance. The most 



4-5 



is often used to manufacture parts which will 
be subjected to acids and saltwater and for 
such parts as ball bearings, shafts and valve stems 
in applications involving high-pressure and high 
temperature. 

VANADIUM. Vanadium is added in small 
quantities to steel to increase tensile strength, 
toughness, and wear resistance. It is most 
often combined with chromium and is used for 
crankshafts, axles, piston rods, springs, and other 
parts where high strength and fatigue resistance 
are required. Greater amounts of vanadium are 
added to high-speed steel cutting tools to 
prevent tempering of their cutting edges when 
high temperatures are generated by the cutting 
action. 

NICKEL. Nickel is added to steel to increase 
corrosion resistance, strength, toughness, and 
wear resistance. Nickel is used in small amounts 
in the steel for armor plating of a ship due to its 
resistance to cracking when penetrated. Greater 
amounts of nickel are added to chromium to 
produce a metal which withstands severe work- 
ing conditions. Crankshafts, rear axles, and other 
parts subjected to repeated shock are made from 
nickel chrome steel. 

MOLYBDENUM. Molybdenum is added to 
steel to increase toughness, hardenability, shock 
resistance and resistance to softening at high 
temperatures. Molybdenum steel is used for 
transmission gears, heavy duty shafts, and 
springs. Carbon molybdenum (CMo) and chrome 
molybdenum (CrMo) are two alloy steels with 
molybdenum added that are widely used in high 
temperature piping systems in Navy ships. 
Relatively large amounts of molybdenum are used 
to form some of the cutting tools used in the 
machine shop. 

TUNGSTEN. Tungsten is used primarily in 
high-speed steel or cemented carbide cutting tools. 
It is this alloy that gives the cutting tools 
their hard, wear resistant and heat resistant 
characteristics. Tungsten has the additional 
property of being air-hardening and allows tools 
to be hardened without using oil or water to cool 
the tool after heating. 



are included among me nonierrous metals. You 
will find that these metals, and their alloys such 
as brass, bronze, copper-nickel, and so on, are 
used in large amounts in the construction and 
maintenance of Navy ships. 

Copper Alloys 

Copper is a metal which lends itself to a variety 
of uses. You will see it aboard ship in the form 
of wire, rod, bar, sheet, plate, and pipe. As a 
conductor of both heat and electricity, copper 
ranks next to silver; it also offers a high resistance 
to saltwater corrosion. 

Copper becomes hard when worked but can 
be softened easily by being heated to a cherry red 
and then cooled. Its strength, however, decreases 
rapidly at temperatures above 400 F. 

Pure copper is normally used in molded or 
shaped forms when machining is not required. 
Copper for normal shipboard use generally is 
alloyed with an element that provides good 
machinability characteristics. 

BRASS. Brass is an alloy of copper and zinc. 
Complex brasses contain additional alloying 
agents, such as aluminum, lead, iron, manganese, 
or phosphorus. Naval brass is a true brass 
containing about 60% copper, 39% zinc, and 1% 
tin added for corrosion resistance. It is used for 
propeller shafts, valve stems, and marine 
hardware. 

Brass used by the Navy is classified as either 
leaded or unleaded, meaning that small amounts 
of lead may or may not be used in the copper- 
zinc mixture. The addition of lead improves the 
machinability of brass. 

BRONZE. Bronze is primarily an alloy of 
copper and tin, although several other alloying 
elements are added to produce special bronze 
alloys. Aluminum, nickel, phosphorous, silicon 
and manganese are the most widely used alloy- 
ing metals. Some of the more common alloys, 
their chemical analyses and some general uses are 
listed in the following paragraphs to give you an 
idea of how basic bronze is changed. 

GUN METAL. Gun metal, a copper-tin 
alloy, contains approximately 86%-89% copper 
(Cu), 7 l/2%-9% tin (Sn), 3%-5% zinc Zn), 
0.3% lead (Pb), 0.15% iron (Fe), 0.05% 



4-6 



alloy, the term "copper-tin" is used only to 
designate the major alloying elements. Gun metal 
bronze is used for bearings, bushings, pump 
bodies, valves, impellers, and gears. 

ALUMINUM BRONZE. Aluminum bronze 
is actually a copper-aluminum alloy that does not 
contain any tin. It is made of 86% copper, 
8 l/2%-9% aluminum (Al), 2 l/2%-4% iron 
and 1% of miscellaneous alloys. It is used for 
valve seats and stems, bearings, gears, propellers, 
and marine hardware. 

COPPER-NICKEL. Copper-nickel alloy is 
used extensively aboard ship because of its high 
resistance to the corrosive effects of saltwater. It 
is used in piping and tubing. In sheet form it is 
used to construct small storage tanks and hot 
water reservoirs. Copper-nickel alloy may contain 
either 70% copper and 30% nickel or 90% 
copper and 10% nickel. It has the general working 
characteristics of copper but must be worked cold. 

These and the many other copper alloys 
commonly used by the Navy have certain physical 
and mechanical properties (imparted by the 
various alloying elements) which cause one alloy 
to be more effective than another for a given 
application. Remember this if you go to the metal 
storage rack and select a bronze-looking metal 
without regard to the specific type. The part you 
make may fail prematurely in spite of the skill and 
attention to detail that you use to machine it. 



Nickel Alloys 

Nickel is a hard, malleable, and ductile metal. 
It is resistant to corrosion and therefore often is 
used as a coating on other metals. Combined with 
other metals, it makes a tough strong alloy. 

NICKEL-COPPER, Nickel-copper alloys 
are stronger and harder than either nickel or 
copper. They have high resistance to corrosion 
and are strong enough to be substituted for 
steel when corrosion resistance is of primary 
importance. Probably the best known nickel- 
copper alloy is Monel (the trademark for a 
product of the International Nickel Company). 
Monel contains approximately 65% nickel, 30% 
copper, and a small percentage of iron, 
manganese, silicon, and cobalt. Monel is used for 
pump shafts and internal parts, valve seats and 



K-MONEL. K-Monel, also a trademark, is 
essentially the same as Monel except that it con- 
tains about 3% aluminum and is harder and 
stronger than other grades of Monel. K-Monel 
stock is very difficult to machine; however, you 
can improve the metal's machinability con- 
siderably by annealing it immediately before 
machining. K-Monel is used for the shaft sleeves 
on many pumps because of its resistance to the 
heating and rubbing action of the packing. 

There are several other nickel alloys that you 
may find used in Navy equipment. INCONEL, 
INCONEL-X; H, S, R, and KR MONEL are a 
few of the more common alloys. 

Aluminum Alloys 

Aluminum is being used more and more in 
ship construction because of light weight, easy 
workability, good appearance, and other desirable 
properties. Pure aluminum is soft and not very 
strong. When alloying elements such as 
magnesium, copper, nickel, and silicon are added, 
however, a much stronger metal is produced. 

Each of the aluminum alloys has properties 
developed specifically for a certain type of 
application. The hard aluminum alloys are easier 
to machine than the soft alloys and often are equal 
to low carbon steel in strength. 

Zinc Alloys 

Zinc is a comparatively soft, yet somewhat 
brittle metal. Its tensile strength is only slightly 
greater than that of aluminum. Because of its 
resistance to corrosion, zinc is used as a 
protective coating for less corrosion resistant 
metals, principally iron and steel. There are 
three methods of applying a zinc coating: 
(1) electroplating in a zinc-acid solution; (2) hot 
dipping, in which the metal is dipped into a bath 
of molten zinc; (3) sherardizing, in which zinc is 
reduced to a gaseous state and deposited on the 
base metal. 

Pure zinc, having a strong anodic potential, 
is used to protect the hulls of steel ships against 
electrolysis between dissimilar metals caused by 
electric currents set up by saltwater. Zinc plates 
bolted on the hull, especially near the propellers, 
decompose quite rapidly, but in doing so, greatly 
reduce localized pitting of the hull steel. 



4-7 



parts used in electrical appliances. This alloy is 
often mistakenly referred to as the copper and 
lead alloy called "pot-metal." 

Tin Alloys 

Pure tin is seldom used except as a coating for 
food containers, sheet steel and in some applica- 
tions involving electroplating to build up the metal 
surfaces of some equipment (motor end bell bear- 
ing housings). Several different grades of tin 
solder are made by adding either lead or 
antimony. One of the primary uses of tin by the 
Navy is to make bearing babbitt. About 5% 
copper and 10% antimony are added to 85% tin 
to make this alloy. There are various grades of 
babbitt used in bearings and each grade may have 
additional alloying elements added to give the 
babbitt the properties required. 

Lead Alloys 

Lead is probably the heaviest metal with 
which you will work. A cubic foot of it weighs 
approximately 700 pounds. It has a grayish color 
and is amazingly pliable. It is obtainable in sheets 
and pigs. The sheets normally are wound around 
a rod and pieces can be cut off quite easily. One 
of the most common uses of lead is as an alloying 
element in soft solder. 



DESIGNATIONS AND MARKINGS 

OF METALS 

You must have knowledge of the standard 
designations of metals and the systems of marking 
metals used by the Navy and industry so you can 
select the proper material for a specific job. There 
are several different numbering systems currently 
in use by different trade associations, societies, 
and producers of metals and alloys that you may 
find on blueprints and specifications of equipment 
that you will be required to repair. You may find 
several different designations which refer to a 
metal with the same chemical composition, or 
several identical designations which refer to metals 
with different chemical compositions. A book 
published by the Society of Automotive 
Engineers, Inc. (SAE), entitled Unified Number- 
ing System of Metals and Alloys and Cross Index 
of Chemically Similar Specifications, provides a 



of the numbering systems that you may need to 
identify are: 

Aluminum Association (AA) 
American Iron and Steel Institute (AISI) 
Society of Automotive Engineers (SAE) 
Aerospace Materials Specifications (AMS) 
American National Standards Institute (ANSI) 

American Society of Mechanical Engineers 
(ASME) 

American Society for Testing and Materials 
(ASTM) 

Copper Development Association (CD A) 

Military Specification (MIL-S-XXXX, MIL- 

N-XXXX) 

Federal Specification (QQ-N-XX, QQ-S- 

XXX) 

The Unified Numbering System, which is 
presented in the book, lists all the different 
designations for a metal and assigns one number 
that identifies the metal. This system of number- 
ing covers only the composition of the metal and 
not the condition, quality or form of the metal. 
Use of the Unified Numbering System by the 
various metal producers is voluntary and it could 
be some time before any widespread uses is 
evident. (Another publication that will be useful 
is NAVSEA 0900-LP-038-8010, Ship Metallic 
Material Comparison and Use Guide.) 

The two major systems used for iron and steel 
are those of the Society of Automotive Engineers 
(SAE) and the American Iron and Steel Institute 
(AISI). The Aluminum Association method is 
used for aluminum; other nonferrous metals are 
designated by the percentage and types of 
elements in their composition. The Navy uses 
these methods of designation as a basis for 
marking metals so they can be identified readily. 

FERROUS METAL DESIGNATIONS 

You should be familiar with the SAE and AISI 
systems of steel classifications. These systems, 



4-8 



the steel. The major difference between the two 
systems is that the AISI system normally uses a 
letter before the numbers to show the process used 
in making the steel. The letters used are as follows: 
B Acid Bessemer carbon steel; C Basic open- 
hearth or basic electric furnace carbon steel; and 
E Electric furnace alloy steel. Example: 



SAE 



AISI 



10 



10 



20 



20 



1 t t 



Basic Open 

Hearth Carbon 

Steel 



Plain Carbon 
Steel 



Carbon 
Content 



A description of these numbering systems is 
provided in the following paragraphs. 

The first digit normally indicates the basic type 
of steel. The different groups are designated as 
follows: 

1 Carbon steel 

2 Nickel steel 

3 Nickel-chromium steel 

4 Molybdenum steel 

5 Chromium steel 

6 Chromium-vanadium steel 

8 Nickel-chrome-molybdenum steel 

9 Silicon-manganese steel 

The second digit normally indicates a series 
within the group. The term "series" usually refers 
to the percentage of the major alloying element. 
Sometimes the second digit gives the actual 
percentage of the chief alloying element; in other 
cases, the second digit may indicate the relative 
position of the series in a group without reference 
to the actual percentage. 

The third, fourth, and fifth digits indicate the 
average carbon content of the steel. The carbon 
content is expressed in points; for example: 
2 points = 0.02%, 20 points = 0.20%, and 
100 points = 1.00%. To make the various steels 
fit into this classification, it is sometimes necessary 
to vary the system slightly. However, you can 



(1) SAE 1035: The first digit is 1, so this is 
a carbon steel. The second digit, 0, indicates that 
there is no other important alloying element; 
hence, this is a PLAIN carbon steel. The next 
two digits, 35, indicate that the AVERAGE 
percentage of carbon in steels of this series is 
0.35%. There are also small amounts of other 
elements in this steel, such as manganese, 
phosphorus, and sulfur. 

(2) SAE 1146: This is a resulfurized carbon 
steel (often called free cutting steel). The first digit 
indicates a carbon steel with an average 
manganese content of 1.00% and an average 
carbon content of 0.46%. The amount of sulfur 
added to this steel ranges from 0.08% to 0.13%. 
These two elements, (manganese and sulfur) in 
this great a quantity make this series of steel one 
of the most easily machined steels available. 

(3) SAE 4017: The first digit, 4, indicates that 
this is a molybdenum steel. The second digit, 0, 
indicates that there is no other equally important 
alloying element; hence, this is a plain 
molybdenum steel. The last two digits, 17, indicate 
that the average carbon content is 0.17%. 

Other series within the molybdenum steel 
group are indicated by the second digit. If the 
second digit is 1, the steel is chromium- 
molybdenum steel; if the second digit is 3, the steel 
is a nickel-chromium-molybdenum steel; if the 
second digit is 6, the steel is a nickel-molybdenum 
steel. In such cases, the second digit does not 
indicate the actual percentage of the alloying 
elements, other than molybdenum. 

(4) SAE 51100: This number indicates a 
chromium steel (first digit) with approximately 
1.0% chromium (second digit) and an average 
carbon content of 1.00% (last three digits). The 
actual chromium content of SAE 51 100 steels may 
vary from 0.95% to 1.10%. 

(5) SAE 52100: This number indicates a 
chromium steel (first digit) of a higher alloy series 
(second digit) than the SAE 51100 steel just 
described. Note, however, that in this case the 
second digit, 2, merely identifies the series but 
does NOT indicate the percentage of chromium. 
A 52100 steel will actually have from 1.30% to 
1.60% chromium with an average carbon content 
of 1.00% (last three digits). 



4-9 



The current commonly used tool steels are 
classified by the American Iron and Steel Institute 
into seven major groups and each commonly 
accepted group or subgroup is assigned an 
alphabetical letter. Methods of quenching, 
applications, special characteristics, and steels for 
particular industries are considered in this type 
classification of tool steels as follows: 

Group Symbol and type 

Water hardening ---- W 
Shock resisting ...... S 

!O Oil hardening 
A Medium alloy 
D High carbon-high-chromium 

Hot work .......... H (HI to H19 incl. chromium 

base, H20 to H39 incl. 
tungsten base, H40 to H59 
incl. Molybdenum base) 



High-speed 



( Jr- 
[ M 



base 
Molybdenum base 



Special purpose ..... (L-Low alloy 
I F 



Carbon tungsten 



Mold steels ......... P 



Navy blueprints and the drawings of equip- 
ment furnished in the manufacturers' technical 
manuals usually specify materials by Federal or 
Military specification numbers. For example, the 
coupling on a particular oil burner is identified 
as "cast steel, class B, MIL-S-15083." This 
particular cast steel does not have any other 
designation under the various other metal 
identification systems as there are no chemically 
similar castings. On the other hand, a valve stem 
which has a designated material of "MIL-S-862 
class 410" (a chromium stainless steel) may be 
cross referenced to several other systems. Some 
of the chemically similar designations for "MIL- 
S-862 class 410" are as follows: 

SAE = J405 (51410) 

Federal Spec. = QQ-S-763(410) 

AISI = 410 

ASTM = A176(410) 

ASM = 5504 

ASME = SA194 



NONFERROUS METAL 
DESIGNATIONS 

Nonferrous metals are generally grouped 
according to the alloying elements. Examples of 
these groups are brass, bronze, copper-nickel, and 
nickel-copper. Specific designations of an alloy 
are described by the amounts and chemical 
symbols of the alloying elements. For example, 
a copper-nickel alloy might be described as 
copper-nickel, 70 Cu-30 Ni. The 70 Cu represents 
the percentage of copper, and the 30 Ni represents 
the percentage of nickel. 

Common alloying elements and their symbols 
are: 

Aluminum Al 

Carbon C 

Chromium Cr 

Cobalt Co 

Copper Cu 

Iron Fe 

Lead Pb 

Manganese Mn 

Molybdenum Mo 

Nickel Ni 

Phosphorus P 

Silicon Si 

Sulphur S 

Tin Sn 

Titanium Ti 

Tungsten W 

Vanadium V 

Zinc Zn 

In addition to the type of designations 
previously described, a trade name (such as Monel 
or Inconel) is sometimes used to designate certain 
alloys. 



system described for steels. The numerals 
assigned, with their meaning for the first digits 
of this system, are: 

Aluminum (99.00% minimum Ixxx 
and greater) 

Major Alloying Element 

Copper 2xxx 

Manganese 3xxx 

Silicon 4xxx 

Magnesium 5xxx 

Magnesium and silicon 6xxx 

Zinc 7xxx 

Other element 8xxx 

The first digit indicates the major alloying element 
and the second digit indicates alloy modifications 
or impurity limits. The last two digits identify the 
particular alloy or indicate the aluminum purity. 

In the Ixxx group for 99.00% minimum 
aluminum, the last two digits indicate the 
minimum aluminum percentage to the right of the 
decimal point. The second digit indicates 
modifications in impurity limits. If the second 
digit in the designation is zero, there is no 
special control on individual impurities. Digits 
1 through 9, indicate some special control of one 
or more individual impurities. As an example, 
1030 indicates a 99.30% minimum aluminum 
without special control on individual impurities, 
and 1 130, 1230, 1330, and so on indicate the same 
purity with special control of one or more 
individual impurities. 

Designations 2 through 8 are aluminum alloys. 
In the 2xxx through 8xxx alloy groups, the second 
digit in the designation indicates any alloy 
modification. The last two of the four digits in 
the designation have no special significance but 
serve only to identify the different alloys in the 
group. 

In addition to the four-digit alloy designation, 
a letter or letter/number is included as a temper 
designation. The temper designation follows the 
four-digit alloy number and is separated from it 



solution neat treated, 
then artificially aged; T6 is the temper designa- 
tion. The aluminum alloy temper designations and 
their meanings are: 

W Fabricated 

O Annealed recrystallized (wrought only) 

H Strain hardened (wrought only) 

HI, plus one or more digits, strain 
hardened only 

H2, plus one or more digits, strain 
hardened then partially annealed 

H3, plus one or more digits, strain 
hardened then stabilized 

W Solution heat treated unstable temper 

T Treated to produce stable tempers other 
than F, O, or H 

T2 Annealed (cast only) 

T3 Solution heat treated, then cold 
worked 

T4 Solution heat treated and naturally 
aged to a substantially stable condi- 
tion 

T5 Artificially aged only 

T6 Solution heat treated, then artifi- 
cially aged 

T7 Solution heat treated, then stabilized 

T8 Solution heat treated, cold worked, 
then artificially aged 

T9 Solution heat treated, artificially 
aged, then cold worked 

T10 Artificially aged, then cold worked 

Note that some temper designations apply only 
to wrought products, others to cast products, but 
most apply to both. A second digit may appear 
to the right of the mechanical treatment. This 
second digit indicates the degree of hardening; 
2 is 1/4 hard, 4 is 1/2 hard, 6 is 3/4 hard, and 
8 is full hard. For example, the alloy 5456-H32 
is an aluminum/magnesium alloy, strain hardened 
then stabilized, and 1/4 hard. 



STANDARD MARKING OF METALS 

Metals used by the Navy are usually marked 
with the continuous identification marking 



4-11 



system. This system will be explained in the 
following paragraphs. Do not depend only on the 
markings to ensure that you are using the correct 
metal. Often, the markings provided by the metal 
producer will be worn off or cut off and you are 
left with a piece of metal that you are not sure 
about. Additional systems, such as separate 
storage areas or racks for different types of metal 
or etching on the metal with an electric etcher 
could save you time later on. 

CONTINUOUS IDENTIFICATION 
MARKING 

The continuous identification marking system, 
which is described in Federal Standards is a means 
for positive identification of metal products even 
after some portions have been used. In the 
continuous identification marking system, the 
markings appear at intervals of not more than 3 
feet. Thus, if you cut off a piece of bar stock, 
the remaining portions will still carry the proper 
identification. Some metals, such as small tubing, 



coils of wire, and small bar stock cannot be 
marked readily by this method. On these items, 
tags with the required marking information are 
fastened to the metal. 

The continuous identification marking is 
actually "printed" on the metals with a heavy ink 
that is almost like a paint. 

The manufacturer is required to make these 
markings on materials before delivery. The mark- 
ing intervals for various shapes and forms, are 
specified in the Federal Standard previously 
mentioned. Figure 4-1 shows the normal spacing 
and layout. 

For metal products, the continuous identifica- 
tion marking must include (1) the producer's name 
or registered trademark and (2) the commercial 
designation of the material. In nonferrous metals 
the government specification for the material is 
often used. The producer's name or trademark 
shown is that of the producer who performs the 
final processing or finishing operation before the 
material is marketed. The commercial designation 
includes (1) a material designation such as an SAE 



BARS 



PRODUCERS NAME 
OR TRADEMARK 1035 AQ NORM HT 69321 




HEAT OR PROCESSING NUMBER 
(NORMALLY USED BY MANUFACTURER) 



PHYSICAL CONDITION 



COMMERCIAL DESIGNATION 



SHEET 
8' 



PRODUCER S NAME 
OR TRADEMARK MIL-S-7809 HT6875 



PRODUCERS NAME 
OR TRADEMARK MIL-S-7809 HT6875 



PRODUCER S NAME 
OR TRADEMARK MIL-S-7809 HT6875 




IN SOME CASES, COMMERCIAL DESIGNATIONS 
ARE USED INSTEAD OF SPECIFICATIONS 



designation that is, the designation of temper 
or other physical condition approved by a 
nationally recognized technical society or 
industrial association such as the American 
Iron and Steel Institute. Some of the physical 
conditions and quality designations for various 
metal products are listed below: 

CR cold rolled 

CD cold drawn 

HR hot rolled 

AQ aircraft quality 

CQ commercial quality 

1/4H quarter hard 

1/2H half hard 

H hard 

HTQ high tensile quality 

AR as rolled 

HT heat treated 

G ground 



lead, zinc, and aluminum have certain identifying 
characteristics surface appearance and weight- 
by which persons who work with or handle these 
materials readily distinguish one from another. 
There are, however, a number of related alloys 
which resemble each other and their base metal 
so closely that they defy accurate identification 
by simple means. 

There are other means of rapid identification 
of metals. These methods, however, do not 
provide positive identification and should not be 
used in critical situations where a specific metal 
is required. Some of the methods that will be 
discussed here are magnet tests, chip tests, file 
tests, acid reaction tests, and spark tests. The latter 
two are the most commonly used by the Navy. 
Table 4-2 contains information related to surface 
appearance, magnetic reaction, lathe chip test, 
and file test. The acid test and the spark test are 
discussed in more detail in the next sections. When 
you perform these tests, you should have a known 
sample of the desired material and make a 



Table 4-2. Rapid Identification of Metals 



Metal 


Surface Appearance 
or markings 


Reaction to a 
Magnet 


Lathe Chip test 


Color of freshly 
filed surface 


White cast Iron 


Dull gray 


Strong 


Short, crumbly chips 


Silvery white 


Gray cast Iron 


Dull gray 


Strong 


Short, crumbly chips 


Light silvery gray 


Aluminum 


L/lght gray to white 
dull or brilliant 


None 


Easily cut, smooth 
ong chips 


White 


Brass 


Yellow to green or 
brown 


None 


Smooth long chips 
slightly brittle 


Reddish yellow to 
yellowish white 


Bronze 


Red to brown 


tone 


Short crumbly 
chips 


Reddish yellow to 
yellowish white 


Copper 


Smooth; red brown 
to green (oxides) 


None 


Smooth long pliable 
chips 


Bright copper 
color 


Copper-nickel 


Smooth; gray to 
yellow or yellowish 
green 


Mono 


Smooth, continuous 
chips 


Bright silvery 
white 


Lead 


White to gray; 
smooth, velvety- 


None 


Cut by knife, any 
shape chip 


White 


Nickel 


Dark gray; smooth; 
sometimes green 
(oxides) 


Medium 


Cuts easily, smooth 
continuous chip 


Bright silvery 
white 


Nickel-copper 


Dark gray, smooth 


Very slight 


Continuous chip; 
tough to cut 


Light gray 


Plain carbon steel 


Dark gray; may be 
rusty 


Strong 


Varies depending 
upon carbon content 


Bright silvery 
gray 


Stainless steel (18-8) 
(25-20) "Note 1 below" 


Dark gray, dull to 
brilliant; usually 
clean 


None (faint If 
severely cold 
worked) 


Varies depending 
upon heat treatment 


Bright silvery 
gray 


Zinc 


Whitish blue, may 
be mottled 


None 


Easily cut; long 
stringy chips 


White 



l ' Stainless steels that have less than 26 percent alloying elements react to magnet. 

4-13 



comparison. You will also need good lighting, a 
strong permanent magnet, and access to a lathe. 
A word of caution: when you perform these tests, 
DO NOT be satisfied with the results of only one 
test. Use as many tests as possible so you can 
increase the chances of making an accurate 
identification. 



SPARK TEST 

Spark testing is the identification of a metal 
by observing the color, size, and shape of the 
spark stream given off when the metal is held 
against a grinding wheel. This method of 
identification is adequate for most machine shop 
purposes. When the exact composition of a metal 
must be known, a chemical analysis must be 
made. Identification of metals by the spark test 
method requires considerable experience. To gain 
this experience, you will need to practice by 
comparing the spark stream of unknown 
specimens with that of sample specimens of 
known composition. Many shops maintain 
specimens of known composition for comparison 
with unknown samples. 

Proper lighting conditions are essential for 
good spark testing practice. You should perform 
the test in an area where there is enough light, but 
should avoid harsh or glaring light. In many ships 
you may find that a spark test cabinet has been 
erected. Generally, these cabinets consist of a box 
mounted on the top of a workbench and have a 
dark painted interior. A bench grinder is mounted 
inside the cabinet. Test specimens of known 
composition are contained in shelves at the end 
of the cabinet. Where possible, the testing area 
should be away from heavy drafts of air, because 
air drafts can change the tail of the spark stream 
and may result in improper identification of the 
sample. 

The speed of the grinding wheel and the 
pressure you exert on the samples greatly affect 
the spark test. The faster the speed of the wheel, 
the larger and longer the spark stream will be. 
(Generally speaking, a suitable grinding wheel for 
spark testing is an 8-inch wheel turning at 3600 
rpm. This provides a surface speed of 7,537 feet 
per minute.) The pressure of the piece against the 
wheel has a similar effect: the more pressure 
applied to the test piece, the larger and longer the 
spark stream will be. Hold the test piece lightly 
but firmly against the wheel with just enough 
pressure to prevent the piece from bouncing. 
Remember, you must apply the same amount of 



pressure to the test specimen as to the sample 
are testing. 

The grain size of the grinding wheel sh< 
be from 30 to 60 grains. Be sure to keep the \\ 
clean at all times. A wheel loaded with part 
of metal will give off a spark stream of the 
of metal in the wheel mixed with the spark sti 
of the metal being tested. This will ten< 
confuse you and prevent you from proi 
identifying the metal. Dress the wheel before 
begin spark testing and before each new tei 
a different metal. 

The spark test is made by holding a sai 
of the material against a grinding wheel. 
sparks given off, or the lack of sparks, assi 
identifying the metal. The length of the s; 
stream, its color, and the type of sparks an 
features for which you should look. Then 
four fundamental spark forms produced wh 
sample of metal is held against a power grir 
(See fig. 4-2.) Part A shows shafts, b 
breaks, and arrows. The arrow or spearhe; 
characteristic of molybdenum, a metallic elei 
of the chromium group which resembles iron 
is used for forming steel-like alloys with car 





Figure 4-2. Fundamental spark forms. 



shows shafts and sprigs or sparklers which indicate 
a high carbon content. Part C shows shafts, forks, 
and sprigs which indicate a medium carbon 
content. Part D shows shafts and forks which 
indicate a low carbon content. 

The greater the amount of carbon present in 
a steel, the greater the intensity of bursting that 
will take place in the spark stream. To under- 
stand the cause of the bursts, remember that while 
the spark is glowing and in contact with the 
oxygen of the air, the carbon present in the 
particle is burned to carbon dioxide (CO 2 ). As the 
solid carbon combines with oxygen to form COa 
in the gaseous state, the increase in volume builds 
up a pressure that is relieved by an explosion of 
the particles. If you examine the small steel 
particles under a microscope when they are cold, 
you will see that they are hollow spheres with one 
end completely blown away. 

Steels having the same carbon content but 
different alloying elements are not always easily 
identified because alloying elements affect the 
carrier lines, the bursts, or the forms of 
characteristic bursts in the spark picture. The 
effect of the alloying element may retard or 
accelerate the carbon spark or make the carrier 
line lighter or darker in color. Molybdenum, for 
example, appears as a detached, orange-colored, 
spearhead on the end of the carrier line. Nickel 
seems to suppress the effect of the carbon burst. 
But the nickel spark can be identified by tiny 
blocks of brilliant white light. Silicon suppresses 
the carbon burst even more than nickel. When 
silicon is present, the carrier line usually ends 
abruptly in a flash of white light. 

To make the spark test, hold the piece of metal 
on the wheel so that you throw the spark stream 
about 12 inches at a right angle to your line of 
vision. You will need to spend a little time to 
discover at just what pressure you must hold the 
sample to get a stream of this length without 
reducing the speed of the grinder. Do not press 
too hard because the pressure will increase the 
temperature of the spark stream and the burst. 
It will also give the appearance of a higher carbon 
content than that of the metal actually being 
tested. After practicing to get the feel of correct 
pressure on the wheel until you are sure you have 
it, select a couple of samples of metal with widely 
varying characteristics; for example, low-carbon 



careful to strike the same portion of the wheel 
with each piece. With your eyes focused at a point 
about one-third the distance from the tail end of 
the stream of sparks, watching only those sparks 
which cross the line of vision, you will find that 
after a little while you will form a mental image 
of the individual spark. After you can fix the 
spark image in mind, you are ready to examine 
the whole spark picture. 

Notice that the spark stream is long (about 70 
inches normally) and that the volume is 
moderately large in low-carbon steel, while in high 
carbon steel the stream is shorter (about 55 inches) 
and large in volume. The few sparklers which may 
occur at any place in low carbon steel are forked, 
while in high carbon steel the sparklers are small 
and repeating and some of the shafts may be 
forked. Both will produce a white spark stream. 

White cast iron produces a spark stream 
approximately 20 inches long (see fig. 4-3). The 
volume of sparks is small with many small, 
repeating sparklers. The color of the spark stream 
close to the wheel is red, while the outer end of 
the stream is straw-colored. 

Gray cast iron produces a stream of sparks 
about 25 inches long. It is small in volume with 
fewer sparklers than in the stream from white cast 
iron. The sparklers are small and repeating. Part 
of the stream near the grinding wheel is red, and 
the outer end of the stream is straw-colored. 

The malleable iron spark test will produce a 
spark stream about 30 inches long. It is of 
moderate volume with many small, repeating 
sparklers toward the end of the stream. The 
entire stream is straw-colored. 

The wrought iron spark test produces a spark 
stream about 65 inches long. The stream has a 
large volume with few sparklers. The sparklers 
show up toward the end of the stream and are 
forked. The stream next to the grinding wheel is 
straw-colored, while the outer end of the stream 
is a bright red. 

Stainless steel produces a spark stream 
approximately 50 inches long, of moderate 
volume, and with few sparklers. The sparklers are 
forked. The stream next to the wheel is straw- 
colored, while at the end it is white. 



4-15 





LOW CARBON AND CAST STEEL 



MALLEABLE IRON 







GRAY CAST IRON 



WROUGHT IRON 





HIGH CARBON STEEL 



STAINLESS STEEL 




WHITE CAST IRON NICKEL 

Figure 4-3. Spark pictures formed by common metals. 



11.37 



Nickel produces a spark stream only about 10 
inches long. It is small in volume and orange in 
color. The sparks form wavy streaks with no 
sparklers. 

Monel forms a spark stream almost identical 
to that of nickel and must be identified by other 
means. Copper, brass, bronze, and lead form no 
sparks on the grinding wheel, but they are easily 
identified by other means, such as color, 
appearance, and chip tests. 

You will find the spark tests easy and 
convenient to make. They require no special 
equipment and are adaptable to most any 
situation. Here again, experience is the best 
teacher. 

ACID TEST 

The nitric acid test is the most commonly used 
test for metal identification in the Navy today; 



it is used only in noncritical situations. For rapid 
identification of metal, the nitric acid test is one 
of the easiest tests to use and requires no special 
training in chemistry to perform. It is most helpful 
in distinguishing between stainless steel, Monel, 
copper-nickel, and carbon steels. Whenever you 
perform an acid test, be sure to observe the 
following safety precautions. 

NEVER open more than one container of 
acid at one time. 

In mixing, always pour acid slowly into 
water. NEVER pour water into acid because an 
explosion is likely to occur. 

If you spill any acid, dilute it with plenty 
of water to weaken it so it can be safely swabbed 
up and disposed of. 



4-16 



Then wash with a solution of borax and water. 

Wear CLEAR-LENS safety goggles to 
ensure the detection of the reaction of metal to 
an acid test which may be evidenced by a color 
change, the formation of a deposit, or the 
development of a spot. 

Conduct tests in a well-ventilated area. 

To perform the nitric acid test, place one or 
two drops of concentrated (full strength) nitric 
acid on a metal surface that has been cleaned by 
grinding or filing. Observe the resulting reaction 
(if any) for about 2 minutes. Then, add three or 
four drops of water, one drop at a time, and 
continue observing the reaction. If there is no 
reaction at all, the test material may be one of 
the stainless steels. A reaction that results in a 
brown-colored liquid indicates a plain carbon 
steel. A reaction producing a brown to black color 
indicates a gray cast iron or one of the alloy steels 
containing as its principal element either 
chromium, molybdenum, or vanadium. Nickel 
steel reacts to the nitric acid test by forming a 
brown to greenish-black liquid, while a steel 
containing tungsten reacts slowly to form a 
brown-colored liquid with a yellow sediment. 

When nonferrous metals and alloys are sub- 
jected to the nitric acid test, instead of the brown- 
black colors that usually appear when ferrous 
metals are tested, various shades of green and blue 
appear as the material dissolves. Except for 
nickel and Monel, the reaction is vigorous. The 
reaction of nitric acid on nickel proceeds slowly, 
developing a pale green color. On Monel, the 
reaction takes place at about the same rate as on 
ferrous metals, but the characteristic color of the 
liquid is greenish-blue. Brass reacts vigorously, 
with the test material changing to a green color. 
Tin bronze, aluminum bronze, and copper all 
react vigorously in the nitric acid test, with the 
liquid changing to a blue-green color. Aluminum 
and magnesium alloys, lead, lead-silver, and lead- 
tin alloys are soluble in nitric acid, but the blue 
or green color is lacking. 

From the information given thus far, it is easy 
to see that you will need considerable visual skill 
to identify the many different reactions of metals 
to nitric acid. There are acid test kits available 
containing several different solutions to identify 
the different metals. Some of the kits can 
identify between the different series of stainless 



quickly with these tests. A chemical laboratory 
is available in most large repair ships and shore 
repair facilities. The personnel assigned are also 
available to identify various metals in more critical 
situations or when a greater degree of accuracy 
is required on a repair job. 



HEAT TREATMENT 

Heat treatment is the operations, including 
heating and cooling of a metal in its solid state, 
that develop or enhance a particular desirable 
mechanical property, such as hardness, toughness, 
machinability, or uniformity of strength. The 
theory of heat treatment is based upon the effect 
that the rate of heating, degree of heat, and the 
rate of cooling have on the molecular structure 
of a metal. 

There are several forms of heat treating. The 
forms commonly used for ferrous metals are: 
annealing, normalizing, hardening, tempering, 
and case-hardening. Detailed procedures for the 
various heat treatments of metals and the theories 
behind them are beyond the scope of this manual. 
However, since you will run across the terms from 
time to time and will probably perform some of 
the heat treatment processes under the supervision 
of an MR1 or MRC, we will discuss some of the 
general terminology. 

ANNEALING 

The chief purposes of annealing are (1) to 
relieve internal strains and (2) to make a metal 
soft enough for machining. Annealing is the 
process of heating a metal to and holding it at a 
suitable temperature and then cooling it at a 
suitable rate, for such purposes as reducing hard- 
ness, improving machinability, facilitating cold 
working, producing a desired microstructure or 
obtaining desired mechanical, physical or other 
properties. 

Besides rendering metal more workable, 
annealing can also be used to alter other physical 
properties, such as magnetism and electrical 
conductivity. Annealing is often used for 
softening nonferrous alloys and pure metals after 
they have been hardened by cold work. Some of 
these alloys require annealing operations which 
are different from those for steel. 

For ferrous metals, the annealing method most 
commonly used, if a controlled atmosphere 



4-17 



furnace is not available, is to place the metal in 
a cast iron box and cover it with sand or fire clay. 
Packing this material around the metal prevents 
oxidation. The box is then placed in the furnace, 
heated to the proper temperature, held there for 
a sufficient period, and then allowed to cool 
slowly in the sealed furnace. 

Instructions for annealing the more common 
metals: 

CAST IRON: Heat slowly to between 1400 
and 1800F, depending on composition. Hold at 
the specific temperature for 30 minutes, and then 
allow the metal to cool slowly in the furnace or 
annealing box. 

COPPER: Heat to 925 F. Quench in water. 
A temperature as low as 500 F will relieve most 
of the stresses and strains. 

ZINC: Heat TO 400 F. Cool in open, still air. 

ALUMINUM: Heat to 750 F. Cool in open 
air. This reduces hardness and strength but 
increases electrical conductivity. 

NICKEL-COPPER ALLOYS INCLUDING 
MONEL: Heat to between 1400 and 1450 F. 
Cool by quenching in water or oil. 

NICKEL-MOLYBDENUM-IRON and 
NICKEL-MOLYBDENUM-CHROMIUM AL- 
LOYS (Stellate): Heat to between 2100 and 
21 SOT. Hold at this temperature for a suitable 
time, depending on thickness. Follow by rapid 
cooling in a quenching medium. 

BRASS: Annealing to relieve stress may be 
done at a temperature as low as 600 F. Fuller 
anneals may be done with increased temperatures. 
Larger grain size and loss of strength will result 
from too high temperatures. Do NOT anneal at 
temperatures exceeding 1300 F. Slowly cool the 
brass to room temperature. Either wrap the part 
with heat retarding cloth or bury it in slaked lime 
or other heat retarding material. 

BRONZE: Heat to HOOT. Cool in an open 
furnace to SOOT or place in a pan to avoid uneven 
cooling caused by air drafts. 

NORMALIZING 

Normalizing is the process of heating a 
ferrous alloy to a suitable temperature above the 



critical temperature or transformation range (see 
section on hardening) and then cooling in still 
air. Normalizing relieves stresses and strains 
caused by welding, forging and uneven cooling. 
Normalizing also removes the effects of previous 
heat treatments. 

HARDENING 

Cutting tools, chisels, twist drills, and many 
other pieces of equipment and tools must be 
hardened to enable them to retain their cutting 
edges. Surfaces of roller bearings, parallel blocks, 
and armor plate must be hardened to prevent wear 
or penetration. Metals and alloys can be hardened 
in several ways; a brief general description of one 
method of hardening follows: 

Each steel has a critical temperature at which 
a marked change will occur in its grain structure 
and physical properties. This critical temperature 
varies according to the carbon content of the steel. 
To be hardened, steel must be heated to a little 
more than this critical temperature to ensure that 
every point in it will have reached critical 
temperature and to allow for some slight loss of 
heat when the metal is transferred from the 
furnace to the cooling medium. The steel must 
then be cooled rapidly by being quenched in oil, 
freshwater, or brine. Quenching firmly fixes the 
structural changes which occurred during heating 
and thus causes the metal to remain hard. 

If allowed to cool too slowly, the metal will 
lose its hardness. On the other hand, to prevent 
too rapid quenching which would result in 
warping and cracking, it is sometimes necessary 
to use oil instead of freshwater or saltwater for 
high carbon and alloy steels. Saltwater, as 
opposed to freshwater, produces greater hardness. 

To prevent hard and soft spots when quench- 
ing, hold the part with a set of tongs made with 
long handles and grips or jaws that will hold the 
part firmly but with a minimum amount of 
surface contact. When you submerge the part in 
the cooling medium, rapidly move it up and down 
while moving it around the cooling medium 
container in a clockwise or counterclockwise 
direction. 

TEMPERING 

The tempering process relieves strains that are 
brought about in steel during the hardening 



hardened steel to a temperature below the critical 
range, holding this temperature for a sufficient 
time to penetrate the whole piece, and then 
cooling the piece. In this process, ductility and 
toughness are improved, but tensile strength and 
hardness are reduced. 

CASE HARDENING 

Case hardening is a process of heat treating 
by which a hard skin is formed on a metal, while 
the inner part remains relatively soft and tough. 
A metal that is originally low in carbon is packed 
in a substance high in carbon content and heated 
above the critical range. The case hardening 
furnace must give a uniform heat. The length of 
time the piece is left in the oven at this high heat 
determines the depth to which carbon is absorbed. 
A commonly used method of case hardening is 
to (1) carburize the material (an addition of 
carbon during the treatment), (2) allow it to cool 
slowly, (3) reheat, and (4) harden in water. Small 
pieces such as bolts, nuts, and screws, however, 
can be dumped into water as soon as they are 
taken out of the carburizing furnace. 



HARDNESS TEST 

A number of tests are used to measure the 
physical properties of metals and to determine 
whether a metal meets specification requirements. 
Some of the more common tests are hardness 
tests, tensile strength tests, shear strength tests, 
bend tests, fatigue tests, and compression tests. 
Of primary importance to a Machinery Repair- 
man is the hardness test. 

Most metals possess some degree of hard- 
ness that is, the ability to resist penetration by 
another material. Many tests for hardness are 
used; the simplest is the file hardness test. While 
fair estimates of hardness can be made by an 
experienced workman, more consistent quan- 
titative measurements are obtained with standard 
hardness testing equipment. Such equipment 
eliminates the variables of size, shape, and hard- 
ness of the file selected, and of the speed, pressure, 
and angles of the file used by the person 
conducting the test. Before discussing the hard- 
ness test equipment, let us consider hardness itself, 
and the value of such information to a Machinery 
Repairman. 



resistance to machine tool cutting, and resistance 
to bending (stiffness) by wrought products. 
Except for resistance to penetration, these 
characteristics of hardness are not readily 
measurable. Consequently, most hardness tests 
are based on the principle that a hard material 
will penetrate a softer one. In a scientific sense, 
then, hardness is a measure of the resistance of 
a material to penetration or indentation by an 
indenter of fixed size and geometrical shape, 
under a specific load. 

The information obtained from a hardness test 
has many uses. It may be used to compare alloys 
and the effects of various heat treatments on 
them. Hardness tests are useful as a rapid, 
nondestructive method for inspecting and 
controlling certain materials and processes and to 
ensure that heat-treated objects have developed 
the hardness desired or specified. The results of 
hardness tests are useful not only for comparative 
purposes, but also for estimating other properties. 
For example, the tensile strength of carbon and 
low-alloy steels can be estimated from the hard- 
ness test number. There is also a relationship 
between hardness and endurance or fatigue 
characteristics of certain steels. 

Hardness may be measured by many types of 
instruments. The most common are the Rockwell 
and Brinell hardness testers. Other hardness tests 
include the Vickers, Eberbach, Monotron, Tukon, 
and Scleroscope. Since there are many tests and 
the hardness numbers derived are not equivalent, 
the hardness numbers must be designated 
according to the test and the scale used in the test. 
Since you are more likely to have access to a 
Rockwell tester than any other, this method is 
discussed in detail. The essential differences 
between the Rockwell and Brinell tests will also 
be discussed in the sections which follow. In 
addition, the Scleroscope and Vickers hardness 
tests will be covered briefly. 

ROCKWELL HARDNESS TEST 

Of all the hardness tests, the Rockwell is the 
one most frequently used. The basic principle of 
the Rockwell test (like that of the Brinell, Vickers, 
Eberbach, Tukron, and Monotron tests) is that 
a hard material will penetrate a softer one. This 
test operates on the principle of measuring the 
indentation, in a test piece of metal, made by a 
ball or cone of a specified size which is being 
forced against the test piece of metal with specified 



4-19 



pressure. In the Rockwell tester shown in 
figure 4-4, the hardness number is obtained by 
measuring the depression made by a hardened 
steel ball (indenter) or a spheroconical diamond 
penetrator of a given size under a given pressure. 

With the normal Rockwell tester shown, the 
120 spheroconnical penetrator is used in conjunc- 
tion with a 150-kilogram (kg) weight to make 
impressions in hard metals. The hardness number 
obtained is designated Rockwell C (Re). For softer 
metals, the penetrator is a 1/16-inch steel ball used 
in conjunction with a 100-kg weight. A hardness 
number obtained under these conditions is 
designated Rockwell B (Rb). 

Figure 4-5 illustrates the principle of indenter 
hardness tests. Although the conical penetrator 
is shown, the principle is the same for a ball 
penetrator. (The geometry of the indentations 
will, of course, differ slightly.) 

With the Rockwell tester, a deadweight, acting 
through a series of levers, is used to press the ball 
or cone into the surface of the metal to be tested. 
Then the depth of penetration is measured. The 
softer the metal being tested, the deeper the 



SMALL 
POINTER 

HARDNESS 
DIAL- 
LING 
NEEDLE 



INDENTER 
ANVIL 



ELEVATING 
WHEEL 



KNURLED 

ZERO 
ADJUSTER 

DEPRESSOR 
BAR 



WEIGHTS 




102.90 
Figure 4-4. Standard Rockwell hardness testing machine. 



penetration will be under a given load. The 
average depth of penetration on samples of very 
soft steel is only about 0.008 inch. The hardness 
is indicated on a dial, calibrated in the Rockwell 
B and the Rockwell C hardness scales. The harder 
the metal, the higher the Rockwell number will 
be. Ferrous metals are usually tested with the 
spheroconical penetrator, with hardness numbers 
being read from the Rockwell C scale. The steel 
ball is used for nonferrous metals and the results 
are read on the B scale. 

With most indenter-type hardness tests, the 
metal being tested must be sufficiently thick to 
avoid bulging or marking the opposite side. The 
specimen thickness should be at least 10 times the 
depth of penetration. It is also essential that the 
surface of the specimen be flat and clean. When 
hardness tests are necessary on thin material, a 
superficial Rockwell tester should be used. 

The Rockwell superficial tester differs from 
the normal Rockwell tester in the amount of load 
applied to perform the test and in the kind of scale 
used to interpret the results. When the major loads 
on the normal tester are 100 and 150 kg, the major 
loads on the superficial tester are 15, 30, and 45 
kg. One division on the dial gauge of the normal 
tester represents a vertical displacement of the 
indenter of 0.002 millimeter (mm). One division 
of the dial gauge of the superficial tester represents 
a vertical displacement of the indenter of 0.001 
mm. Hardness scales for the Rockwell superficial 
tester are the N and T scales. The N scale is used 
for materials that, if they were thicker, would 
usually be tested with the normal tester using the 
C scale. The T scale is comparable to the B scale 
used with the normal tester'. In other respects the 
normal and superficial Rockwell testers are much 
alike. 

If you have properly prepared a sample and 
have selected the appropriate penetrator and 
weights, you can use the following step-by-step 
procedure to operate a Rockwell tester: 

1 . Place the piece to be tested on the testing 
table, or anvil. 

2. Turn the wheel that elevates the testing 
table until the piece to be tested comes in contact 
with the testing cone or ball. Continue to turn the 
elevating wheel until the small pointer on the 
indicating gauge is nearly vertical and slightly to 
the right of the dot. 

3. Watch the long pointer on the gauge; 
continue raising the work with the elevating wheel 
until the long pointer is nearly upright within 
approximately five divisions, plus or minus, on 



CONE -SHAPED 
PENETRATOR 




THIS INCREASE IN DEPTH OF PENTRATION, CAUSED BY APPLICATION OF MAJOR LOAD, 
FORMS THE BASIS FOR THE ROCKWELL HARDNESS TESTER READINGS. 



Figure 4-5. Principle of Rockwell hardness test. 



126.87 



the scale. This step of the procedure sets the minor 
load. 

4. Turn the zero adjuster, located below the 
elevating wheel, to set the dial zero behind the 
pointer. 

5. Tap the depressor bar downward to release 
the weights and apply the major load. Watch the 
pointer until it comes to rest. 

6. Turn the crank handle upward and for- 
ward, thereby removing the major but not the 
minor load. This will leave the penetrator in 
contact with the specimen but not under pressure. 

7. Observe where the pointer now comes to 
rest and read the Rockwell hardness number on 
the dial. If you have made the test with the 
1/16-inch ball and a 100-kilogram weight, take 
the reading from the red, or B, scale. If you have 
made the test with the spheroconical penetrator 
and a weight of 150 kilograms, take the reading 
from the black, or C scale. (In the first example 
prefix the number by Rb, and in the latter instance 
by Re.) 

8. Turn the hand wheel to lower the anvil. 
Then remove the test specimen. 



BRINELL HARDNESS TEST 

The Brinell hardness testing machine provides 
a convenient and reliable hardness test. The 
machine is not suitable, however, for thin or small 
pieces. This machine has a vertical hydraulic press 
design and is generally hand operated. A lever 
is used to apply the load which forces a 
10-millimeter diameter hardened steel or tungsten- 
carbide ball into the test specimen. For ferrous 
metals, a 3,000-kilogram load is applied. For 
nonferrous metals, the load is 500 kilograms. In 
general, pressure is applied to ferrous metals for 
10 seconds, while 30 seconds is required for 
nonferrous metals. After the pressure has been 
applied for the appropriate time, the diameter of 
the depression produced is measured with a 
microscope having an ocular scale. 

The Brinell hardness number (Bhn) is the ratio 
of the load in kilograms to the impressed surface 
area in square millimeters. This number is found 
by measuring the distance the ball is forced, under 
a specified pressure, into the test piece. The 
greater the distance, the softer the metal, and the 



4-21 



lower the Brinell hardness number will be. 
The width of the indentation is measured 
with a microscope, and the hardness number 
corresponding to this width is found by consulting 
a chart or table. 

The Brinell hardness machine is of greatest 
value in testing soft and medium-hard metals and 
in testing large pieces. On hard steel the imprint 
of the ball is so small that it is difficult to read. 

SCLEROSCOPE HARDNESS TEST 

If you place a mattress on the deck and drop 
two rubber balls from the same height, one on 
the mattress and one on the deck, the one dropped 
on the deck will bounce higher. The reason is that 
the deck is the harder of the two surfaces; this 
is the principle upon which the Scleroscope works. 
When using the Scleroscope hardness test, drop 
a diamond-pointed hammer through a guiding 
glass tube onto the test piece and check the 
rebound (bounce) height on a scale. The harder 
the metal being tested, the higher the hammer will 
rebound, and the higher will be the number on 
the scale. The Scleroscope is portable and can be 
used to test the hardness of pieces too large to be 
placed on the anvil or tables of other machines. 
Since the Scleroscope is portable and can be held 
in the hand, it can be used to test the hardness 
of large guns and marine and other f orgings that 
cannot be mounted on stationary machines. 
Another advantage of the Scleroscope is that it 
can be used without damaging finished surfaces. 
The chief disadvantage, however, of this machine, 
is its inaccuracy. The accuracy of the Scleroscope 
is affected by the following factors: 

1. Small pieces do not have the necessary 
backing and cannot be held rigidly enough to give 
accurate readings. 

2. If large sections are not rigid, if they are 
oddly shaped, if they have overhanging sections, 
or if they are hollow, the readings may be in error. 

3. If oil-hardened parts are tested, oil may 
creep up the glass tube and interfere with the 
drop of the diamond-pointed hammer in the 
instrument, thus causing an error. 

VICKERS HARDNESS TEST 

The Vickers test measures hardness by a 
method similar to that of the Brinell test. The 
indenter, however, is not a ball, but a square- 
based diamond pyramid, which makes it accurate 
for testing thin sheets as well as the hardest steels. 



Up to an approximate hardness number of 
300, the results of the Vickers and the Brinell tests 
are about the same. Above 300, Brinell accuracy 
becomes progressively lower. This divergence 
represents a weakness in the Brinell method a 
weakness that is the result of the tendency of the 
Brinell indenter ball to flatten under heavy loads. 
For this reason, Brinell numbers over 600 are 
considered to be of doubtful reliability. 

If a ship has one type of hardness tester and 
the specifications indicated by the blueprint are 
for another type, a conversion table, such as 
table 4-3, may be used to convert the reading. 

File Hardness Test 

Hardness tests are commonly used to 
determine the ability of a material to resist 
abrasion or penetration by another material. 
Many methods have evolved for measuring the 
hardness of metal. The simplest method is the file 
hardness test. This test cannot be used to make 
positive identification of metals but can be used 
to get a general idea of the type of metal being 
tested and to compare the hardness of various 
metals on hand. Thus, when identification of 
metals by other means is not possible, you can 
use a file to determine the relative hardness of 
various metals. The results of such a test may 
enable you to select a metal suitable for the job 
being performed. 

The file hardness test is simple to perform. 
You may hold the metal being tested in your hand 
and rested on a bench, or put it in a vise. Grasp 
the file with your index finger extended along the 
file and apply the file slowly but firmly to the 
surface being tested. 

If the material is cut by the file with extreme 
ease and tends to clog the spaces between the file 
teeth, it is VERY SOFT. If the material offers 
some resistance to the cutting action of the file 
and tends to clog the file teeth, it is SOFT. If the 
material offers considerable resistance to the file 
but can be filed by repeated effort, it is HARD 
and may or may not have been treated. If the 
material can be removed only by extreme effort 
and in small quantities by the file teeth, it is VERY 
HARD and has probably been heat treated. If the 
file slides over the material and the file teeth are 
dulled, the material is EXTREMELY HARD and 
has been heat treated. 

The file test is not a scientific method. It 
should not be used when positive identification 
of metal is necessary or when an accurate 
measurement of hardness is required. Tests 



4-22 



Hardness 
No. 3,000 kg 


Hardness 
No. C Scale 


Approximate 
Xl,000psi 


Hardness 
No. 3,000 kg 


Hardness 
No. C Scale 


Approximati 
Xl,000psi 




70C 




477 


50.3C 


234 




69C 




461 


48.8C 


226 




68C 




444 


47.2C 


218 




67C 




429 


45.7C 


210 


767 


66.4C 


376 


415 


44.5C 


203 


757 


65.9C 


371 


401 


43. 1C 


196 


745 


65.3C 


365 


388 


41.8C 


190 


733 


64.7C 


359 


375 


40.4C 


184 


722 


64.0C 


354 


363 


39.1C 


178 


710 


63.3C 


348 


352 


37.9C 


172 


698 


62.5C 


342 


341 


36.6C 


167 


682 


61.7C 


334 


331 


35.5C 


162 


670 


61.0C 


328 


321 


34.3C 


157 


653 


60.0C 


320 


311 


33. 1C 


152 


638 


59.2C 


313 


302 


32.1C 


148 


627 


58.7C 


307 


293 


30.9C 


144 


601 


57.3C 


294 


285 


29.9C 


140 


578 


56.0C 


283 


277 


28.8C 


136 


555 


54.7C 


272 


269 


27.6C 


132 


534 


53.5C 


262 


262 


26.6C 


128 


524 


52.1C 


257 


255 


25.3C 


125 


495 


51.0C 


243 









4-23 



Table 4-3. Hardness Conversion Chart (Ferrous Metals) Continued 



Brinell 
Hardness 

No. 500 kg 


Rockwell 
Hardness 
No. B Scale 


Brinell 
Hardness 
No. 500 kg 


Rockwell 
Hardness 
No. B Scale 


201 


99.0B 


143 


85.0B 


195 


98.2B 


140 


82.9B 


189 


97.3B 


135 


80. 8B 


184 


96.4B 


130 


80.0B 


179 


95.5B 


120 


75.B 


175 


94.6B 


110 


70.0B 


171 


93. 8B 


100 


63. 5B 


167 


92.8B 


95 


60.0B 


164 


91. 9B 


90 


56. OB 


161 


90.7B 


85 


52.0B 


158 


90.0B 


80 


47. OB 


156 


89.0B 


75 


41. OB 


153 


87.8B 


70 


34.0B 


149 


86. 8B 


65 


26.0B 


146 


86.0B 







already described should be used for positive 
identification of metals. Special machines, such 
as the Rockwell and Brinell testers, should be used 
when it is necessary to determine accurately the 
hardness of the material. 



PLASTICS 

Plastic materials are being increasingly used 
aboard ship. In some respects, they tend to 
surpass structural metals; plastic has proven to 
be shock resistant, not susceptible to saltwater 
corrosion, and in casting it lends itself to mass 
production and uniformity of end product. 



CHARACTERISTICS 

Plastics are formed from organic materials, 
generally with some form of carbon as their 
basic element. Plastics are referred to as 
synthetic material, but this does not necessarily 
mean that they are inferior to natural material. 
On the contrary, they have been designed 
to perform particular functions that no natural 
material can perform. Plastics can be obtained 
in a variety of colors, shapes, and forms 
some are as tough, but not as hard, as steel; 
some are as pliable as rubber; some are more 
transparent than glass; and some are lighter than 
aluminum. 



4-24 



MOPLASTICS and it is necessary, if you are 
going to perform any kind of shopwork on 
plastics, to know which of these two you are 
using. 

Thermosettings are tough, brittle, and heat 
hardened. When placed in a flame, they will not 
burn readily, if at all. Thermosettings are so hard 
that they resist the penetration of a knife blade; 
any such attempt will dull the blade. If the plastic 
is immersed in hot water and allowed to remain, 
it will neither absorb moisture nor soften. 

Thermoplastics, on the other hand, when 
exposed to heat, become soft and pliable, or even 
melt. When cooled, they retain the shape that they 
took under the application of heat. Some ther- 
moplastics will even absorb a small amount of 
moisture, if placed in hot water. A knife blade 
will cut easily into thermoplastics. 

When testing a plastic by inserting it into a 
fire, you should exercise caution, because ther- 
moplastics will burst into sudden intense flame, 
and give off obnoxious gases. If you use the fire 
test, be sure to hold the plastic piece a considerable 
distance from you. 

MAJOR GROUPS 

While it is not necessary for you to know the 
exact chemical composition of the many plastics 
in existence, it will be helpful to have a general 
idea of the composition of the plastics you are 
most likely to use. Table 4-4 provides informa- 
tion on some groups of plastics which are of 
primary concern to a Machinery Repairman. 

Laminated plastics are made by dipping, 
spraying, or brushing flat sheets or continuous 
rolls of paper, fabric, or wood veneer with resins, 
and then pressing several layers together to get 
hard, rigid, structural material. The number of 
layers pressed together into one sheet of laminated 
plastic will depend upon the thickness desired. The 
choice of paper, canvas, wood veneer, or glass 
fabric will depend upon the end use of the 
product. Paper-based material is thin and quite 
brittle, breaking if bent sharply, but canvas-based 
material is difficult to break. As layers are added 
to paper-based material, it gains in strength, but 
it is never as tough and strong in a laminated part 
as layers of glass fabric or canvas. 

Laminated materials are widely used aboard 
ship. For example, laminated gears are used on 
internal-combustion engines, usually as timing or 
idler gears; on laundry equipment; and on 



heat when friction is generated, and wear longer. 
Plastics are identified by several commercial 
designations, trade names, and by Military and 
Federal specifications. There is such a large 
number of types, grades, and classes of plastics 
within each major group that to rely on the 
recognition of a trade name only would result in 
the wrong material being used. The appropriate 
Federal Supply Catalog should be used to cross 
reference the Military (MIL-P-XXXX) or Federal 
(FED-L-P-XXXX) designations to the correct 
procuring data for the Federal Supply System. 

MACHINING OPERATIONS 

Machining operations that you may perform 
on plastics include cutting parts from sheet or rod 
stock, using various metal cutting saws; removing 
stock from parts by rotating tools as in a drill press 
or a milling machine; cutting moving parts by 
stationary tools, as on a lathe; and finishing 
operations. 

Sawing 

You can use several types of saws bandsaw, 
jigsaw, circular saw to cut blanks from plastic 
stock. Watch the saw speed carefully. Since 
almost none of the heat generated will be carried 
away by the plastic, there is always danger that 
the tool will be overheated to the point that it will 
burn the work. 

Drilling 

In drilling plastics, back the drill out 
frequently to remove the chips and cool the tool. 
A liberal application of kerosene will help keep 
the drill cool. To obtain a smooth, clean hole, use 
paraffin wax on the drill; for the softer plastics, 
you may prefer a special coolant. 

Lathe Operations 

Lathe operations are substantially the same for 
plastics as for metals, except for the type of tool, 
and the manner in which contact is made with the 
work. For plastics, set the tool slightly below 
center. Use cutting tools with zero or slightly 
negative back rake. 

For both thermo settings and thermoplastics, 
recommended cutting speeds are: 200 to 500 fpm 



4-25 



Table 4-4. Major Groups of Plastics 



Plastic 
Trade Names in ( ) 



Advantages and Examples of Uses 



Disadvantages 



Acrylic 
(Lucite, Plexiglass) 



Cellulose nitrate 
(Celluloid) 



Polyamide 

(Nylon) 



Polyethylene 
(Polythene) 



THERMOPLASTICS 

Formability; good impact strength; good aging 
and weathering resistance; high transpar- 
ency, shatter -resistance, rigidity. Used 
for lenses, dials, etc. 

Ease of fabrication; relatively high impact 
strength and toughness; good dimensional 
stability and resilience; low moisture 
absorption. Used for tool handles, mallet 
heads, clock dials, etc. 



High resistance to distortion under load at 
temperatures up to 300 F; high tensile 
strength, excellent impact strength at 
normal temperatures; does not become 
brittle at temperatures as low as minus 
70F; excellent resistance to gasoline and 
oil; low coefficient of friction on metals. 
Used for synthetic textiles, special types 
of bearings, etc. 

Inert to many solvents and corrosive chemi- 
cals; flexible and tough over wide tempera- 
ture range, remains so at temperatures as 
low as minus 100 F; unusually low moisture 
absorption and permeability; high electrical 
resistance; dlmensionally stable at normal 
temperatures; ease of molding; low cost. 
Used for wire and cable insulation, and 
acid resistant clothing. 



Softening point of 170 
to 220 F; low 
scratch resistance. 



Extreme flammabil- 
ity; poor electrical 
insulating prop- 
erties; harder with 
age; low heat dis- 
tortion point. 

Absorption of water; 
large coefficient of 
expansion; relatively 
high cost; weather- 
ing resistance poor. 



Low tensile, co De- 
pressive, flexural 
strength; very high 
elongation at nor- 
mal temperatures; 
subject to spontan- 
eous cracking when 
stored in contact 
with alcohols, 
toluene, and sili- 
cone grease, etc.; 
softens at tem- 
peratures above 
200 F; poor 
abrasion'and cut 
resistance; cannot 
be bonded unless 
given special 
surface treatment. 



Trade Names in ( ) 



Advantages and Examples of Uses 



Disadvantages 



Polytetrafluoroethylene 
(Teflon) 



THERMOPLASTICS 

Extreme chemical inertness; high heat re- 
sistance; nonadhesive; tough; low coefficient 
of friction. Used for preformed packing and 
gaskets. 



Not easily cemented; 
cannot be molded by 
usual methods; gen- 
erates toxic fumes 
at high tempera- 
tures; high cost. 



Phenolformaldehyde 
(Bakelite, Durez, 
Resinox) 



Urea-formaldehyde 
(Beetle, Bakelite 
Urea, Plaskon) 



THERMOSETTING PLASTICS 

Better permanence characteristics than 
most plastics; may be used at temperatures 
from 250 to 475F; good aging resistance; 
good electrical insulating properties; not 
readily flammable, does not support com- 
bustion; inserts can be firmly embedded; 
strong, light; low water absorption; low 
thermal conductivity; good chemical re- 
sistance; economical in production of com- 
plex shapes; free from cold flow; relatively 
insensitive to temperature; low coefficient 
of thermal expansion; no change in dimen- 
sions under a load for a long time; does not 
soften at high temperatures or become 
brittle down to minus 60 F; inexpensive. 
Used for handles, telephone equipment, 
electrical insulators, etc. 

High degree of translucency and light finish; 
hard surface finish; outstanding electrical 
properties when used within temperature 
range of minus 70 to plus 170 F; com- 
plete resistance to organic solvents; 
dimensionally stable under moderate load- 
ings and exposure conditions. Used for 
instrument dials, electric parts, etc. 



Difficult to mold when 
filled for greatest 
impact strength, or 
when in sections less 
than 3/32-inch thick; 
can be expanded or 
contracted by un- 
usually wet or dry 
atmosphere. 



Low impact strength; 
slight warping with 
age; poor water 
resistance. 



4-27 



with high-speed steel tools and 500 to 1500 fpm 
with carbide-tipped tools. 

Finishing Operations 

Plastics must be finished to remove tool marks 
and produce a clean, smooth surface. Usually, 
sanding and buffing are sufficient for this 
purpose. 

You can remove surface scratches and pits by 
hand sandpapering with dry sandpaper of fine 
grit. You can also wet sand by hand, with water 
and abrasive paper of fine grade. If you need to 



remove a large amount of material, use sanding 
wheels or disks. 

After you have removed the pits and scratches, 
buff the plastic. You can do this on a wheel made 
of loose muslin buffs. Use tripoli and rouge 
buffing compounds, depositing a layer of the 
compound on the outside of the buffing wheel. 
Renew the compound frequently. 

When you buff large flat sheets, be careful not 
to use too much pressure, nor to hold the work 
too long in one position. In buffing small plastic 
parts, be careful that the wheel does not seize the 
piece and pull it out of your grasp. 



4-28 



POWER SAWS AND DRILLING MACHINES 



Machine shop work is generally understood 
to include all cold metal work in which a portion 
of the metal is removed by either power driven 
tools or handtools. In your previous studies 
you have become familiar with common hand- 
tools. This chapter and the following chapters 
contain information on power driven, or machine, 
tools. 

The term MACHINE TOOL refers to 
any piece of power driven equipment that 
drills, cuts, or grinds metals and other materials. 
Through the use of attachments, some machine 
tools will perform two or more of these 
operations. Machine tools actually hold and 
work the material. The operator guides the 
mechanical movements by properly setting up 
the work and by adjusting the gearing or 
linkage controls. In this chapter we will 
deal primarily with power saws and drilling 
machines. 



NEVER make adjustments to the saw or 
relocate the stock to be sawed while the 
saw is in operation. 

Keep your hands as far away as possible 
from the saw blade while the saw is in 
operation. 

NEVER attempt to move a large heavy 
piece of stock to or from the saw -without 
help. 

Always support protruding ends of long 
pieces of stock so they will not fall and 
cause injury to either the machine or 
personnel. 

NEVER use bare hands to clean the saw 
cuttings from the machine. 



POWER SAW 
SAFETY PRECAUTIONS 

Before we discuss the operation of power 
saws, you must realize the importance of 
observing safety precautions. Carelessness is one 
of the prime causes of accidents in the machine 
shop. Moving machinery is always a potential 
danger. When this machinery is associated with 
sharp cutting tools, the hazard is greatly increased. 
Some of the more important safety precautions 
are listed here: 



Be alert for sharp burrs on the sawed end 
of stock and remove such burrs with a file 
to prevent injury to personnel. 

Inspect the blade at frequent intervals and 
NEVER use a saw with a dull, pinched, 
or burned blade. 

In all sawing jobs, the golden rule of safety 
is SAFETY FIRST, ACCURACY SEC- 
OND, and SPEED LAST. 



DO NOT operate a power saw that you are 
not fully qualified and authorized to 
operate. 

Wear goggles or a face shield at all times 
when you are operating a power saw. 



POWER HACKSAWS 

The power hacksaw is found in many Navy 
machine shops. It is used for cutting bar stock, 
pipe, tubing, or other metal stock. The power 
hacksaw consists of a base, a saw frame, and a 



5-1 



work-holding device. Figure 5-1 is an illustration 
of a standard power hacksaw. 

The base consists of a reservoir to hold the 
coolant, a coolant pump, the drive motor and a 
transmission for speed selection. Some models 
may have the feed mechanism attached to the 
base. 



The saw frame consists of linkage and a 
circular disk with an eccentric (off center) 
pin designed to convert circular motion into 
reciprocating motion. The blade is inserted 
between the two blade holders and securely 
attached by either hardened pins or socket 
head screws. The inside blade holder is 
adjustable. This adjustable blade holder allows 
the correct tension to be put on the blade 
to ensure that it is held rigidly enough to 
prevent it from wandering and causing a 
slanted cut. The feed control mechanism 
is also attached to the saw frame on many 
models. 

The work holding device is normally a vise 
with one stationary jaw and one movable jaw. The 
movable jaw is mounted over a toothed rack to 




permit a rapid and easy initial adjustment 
close to the material to be cut. Final tightening 
is made by turning the vise screw until 
the material is held securely. An adjustable 
stop permits pieces of the same length to 
be cut without measuring each piece separately. 
A stock support stand (available for both sides 
of the saw) keeps long stock from falling when 
being cut. 

The capacity designation of the power 
hacksaw illustrated is 4 inches x 4 inches. This 
means that it can handle material up to 4 inches 
wide and 4 inches thick. 



BLADE SELECTION 

The blade shown in figure 5-2 is especially 
designed for use with the power hacksaw. It is 
made with a tough alloy steel back and high-speed 
steel teeth, a combination which gives a strong 
blade, and at the same time, a cutting edge 
suitable for high-speed sawing. 

These blades differ by the pitch of the 
teeth (number of teeth per inch). The correct 
pitch of teeth for a particular job is determined 
by the size and material composition of 
the section to be cut. Use coarse pitch teeth 
for wide, heavy sections to provide ample 
chip clearance. For thinner sections, use a 
blade with a pitch that keeps two or more 
teeth in contact with the work so that the teeth 
do not straddle the work. Straddling strips the 
teeth from the blade. In general, select blades 
according to the following information: 

1 . Coarse (4 teeth per inch), for soft steel, cast 
iron, and bronze. 



TOUGH ALLOY 
STEEL BACK 




HIGH SPEED 
STEEL TEETH 



ELECTRIC WELD 



11.18 



Figure 5-1. Standard power hacksaw. 



11.19 



Figure 5-2. Hacksaw blade. 



3. Medium (10 teeth per inch), for solid brass 
stock, iron pipe, and heavy tubing. 

4. Fine (14 teeth per inch), for thin tubing and 
sheet metals. 



COOLANT 

The use of a coolant is recommended for most 
power hacksawing operations. (Cast iron can be 
sawed dry.) The coolant keeps the kerf (narrow 
slot created by the cutting action of the blade) 
clear of chips so that the blade does not bind up 
and start cutting crooked. The teeth of the blade 
are protected from overheating by the coolant, 
permitting the rate of cutting to be increased 
beyond the speed possible when sawing without 
coolant. A soluble oil solution with a mixture of 
the oil and water, made so that no rust problems 
will occur, should be suitable for most sawing 
operations. The normal mixture for soluble oil is 
40 parts water to 1 part oil. 



FEEDS AND SPEEDS 

A power hacksaw will have one of three types 
of feed mechanisms: 

1 . Mechanical feed, which ranges from 0.001 
to 0.025 inch per stroke, depending upon 
the class and type of material being cut. 

2. Hydraulic feed, which normally exerts a 
constant pressure but is designed so that 
when hard spots are encountered the feed 
is automatically stopped or shortened to 
decrease the pressure on the saw until the 
hard spot has been cut through. 

3. Gravity feed, in which weights are placed 
on the saw frame and shifted to give more 
or less pressure of the saw blade against the 
material being cut. 

To prevent unnecessary wear on the back sides 
of the saw blade teeth, the saw frame and blade 
are automatically raised clear of the surface being 
cut on each return stroke. The rate of feed or the 
pressure exerted by the blade on the cutting stroke 



of a hollow pipe, the wall thickness. A hard, large 
diameter piece of stock must be cut with a slower 
or lighter feed rate than a soft, small diameter 
piece of stock. Pipe with thin walls should be cut 
with a relatively light feed rate to prevent stripping 
the teeth from the saw blade or collapsing the 
walls of the pipe. A feed rate that is too heavy 
or fast will often cause the saw blade to wander, 
producing an angled cut. 

The speed of hacksaws is stated in strokes per 
minute, counting only those strokes on which the 
blade comes in contact with the stock. Speed is 
changed by a gear shift lever. There may be a chart 
attached to or near the saw, giving recommended 
speeds for cutting various metals. The following 
speeds, however, can be used: 

1. Medium and low carbon steel, brass, and 
soft metals 136. 

2. Alloy steel, annealed tool steel, and cast 
iron 90. 

3. Unannealed tool steel, and stainless 
steel 60. 



POWER HACKSAW OPERATION 

A power hacksaw is relatively simple to 
operate. There are, however, a few checks you 
should make to ensure good cuts. Support 
overhanging ends of long pieces to prevent 
sudden breaks at the cut before the work is 
completely cut through. Block up irregular shapes 
so that the vise holds firmly. Check the blade to 
ensure that it is sharp and that it is secured at the 
proper tension. 

Place the workpiece in the clamping device, 
adjusting it so the cutting off mark is in line with 
the blade. Turn the vise lever to clamp the material 
in place. Be sure the material is held firmly. 

See that the blade is not touching the 
workpiece when you start the machine. Blades are 
often broken when this rule is not followed. Feed 
the blade slowly into the work, and adjust the 
coolant nozzle so that it directs the fluid over the 
saw blade. 



5-3 



CONTINUOUS FEED CUTOFF SAW 

Figure 5-3 illustrates a type of cutoff saw that 
is now being used throughout the Navy. There are 
different models of this saw, but the basic design 
and operating principles remain the same. 

BAND SELECTION 
AND INSTALLATION 

The bands for the continuous feed cutoff saw 
are nothing more than an endless hacksaw blade. 
With this thought in mind, you can see that all 
the factors that were discussed for power hacksaw 
blade selection can be applied to this saw. This 
saw is also equipped with a band selection chart 



(fig. 5-3) to help you make the proper selection. 
The bands come in two different forms; ready 
made loops of the proper length and coils of 
continuous lengths of 100 feet or more. Nothing 
must be done to the presized band, but the coils 
of saw bands must be cut to the proper length and 
then butt welded. (Butt welding is covered later 
in this chapter.) 

Once you have selected the saw band, install 
it in the following manner: 

1 . Lift the cover on the saw head to expose 
the band wheels. 

2. Place the band on the wheels with the teeth 
down, or toward the deck, and pointing in 
the direction of the band rotation. 



BAND 

SELECTION 

CHART 



BAND 

TENSION 

HANDWHEEL 




VISE 

LOCK 

HANDWHEEL 



28.297X 



This action applies enough tension to hold 
the band on the wheels. When the machine 
is operating, the hydraulic system main- 
tains the proper band tension. 

5. Adjust the saw guides according to the 
manufacturer's manual. Do not set the 
distance between the two guide arms more 
than necessary or the blade will wander. 

6. Select the proper surface speed (feet-per- 
minute), and adjust the V-belt for that 
speed. (See fig. 5-4.) 



-90 F.P.M. 
-125 F.P.M. 
-ISO F.P.M. 
-250 F.P.M. 




DRIVEN 

"PULLEY 



Figure 5-4. Speed change pulley. 



be sawed is held securely in the machine. The 
movement of the saw head is controlled from the 
control panel (fig. 5-5). You can raise, stop, and 
feed the machine with the main control handle. 
The FEED portion of the control is divided into 
vernier and rapid. The RAPID area is used to 
bring the saw band down close to the work; the 
VERNIER controls the feed pressure. Figure 5-5 
shows the vernier control knob with graduations 
from to 9. By using this vernier, you can get 
the maximum cutting efficiency for the type of 
material being cut. When the cut is complete, the 
machine will automatically stop. To raise the head 
above the workpiece for the next cut, push the 
start button and place the control lever in the 
RAISE position. You may have to hold the start 
button down for a second or two until the saw 
head starts to rise. 



METAL CUTTING HANDSAWS 

Metal cutting bandsaws are standard equip- 
ment in repair ships and tenders. These machines 
can be used for nonprecision cutting similar to 
that performed by power hacksaws. Some types 
can be used for precision cutting, filing, and 



O 



o 



O 



o 





o 



o 



28.296X 



Figure 5-5. Control panel (Do AH saw). 



5-5 



polishing. A handsaw has a greater degree of 
flexibility for straight cutting than a power 
hacksaw in that it can cut objects of any 
reasonable size and of regular and irregular 
shapes. A bandsaw also cuts faster than a power 
hacksaw because the cutting action of the blade 
is continuous. 

Figure 5-6 illustrates a metal cutting bandsaw 
with a tillable table. On the type shown, work is 
fed either manually or by power to the blade 
which runs in a fixed position. 

The tillable band type saw is particularly suited 
to taking straight and angle cuts on large, long, 
or heavy pieces. 




The tiltable table type is convenient for 
contour cutting because the angle at which work 
is fed to the blade can be changed readily. This 
machine usually has special attachments and 
accessories for precision inside or outside 
cutting of contours and disks and for mitering 
and has special bands for filing and polishing 
work. 



BANDSAW TERMINOLOGY 

As was previously mentioned, the metal 
cutting bandsaws installed in machine shops in 
tenders and repair ships generally are the tiltable 
table type which can cut, file, or polish work when 
appropriate bands are mounted on the band 
wheels. The saw bands, file bands, and polishing 
bands used on these machines are called BAND 
TOOLS, and the machine itself is often referred 
to as a BAND TOOL MACHINE. Definitions 
which will be helpful in understanding band tool 
terminology are given below for saws, files, and 
polishing bands, in that order. 



SET 



SIDE CLEARANCE 





28.39X 



11.21X 
Figure 5-6. Tiltable (contour) metal-cutting bandsaw. 



Figure 5-8. Set and side clearance. 




GAGE 



L^~ 


LT 




T 1 


RAKER SET PATTERN 

,-_.,./ ,j _r- _ 


I L. 


_ 1^ L 1 


" 


- r i 


WAVE SET PATTERN 



STRAIGHT SET PATTERN 



29.15X 



28.43X 



PITCH: The number of teeth per linear 
inch. 

WIDTH: The distance across the flat face of 
the band. The width measurement is always 
expressed in inches, or fractions of an inch. 

GAUGE: The thickness of the band back. 
This measurement is expressed in thousandths of 
an inch. 

SET: The bend or spread given to the teeth 
to provide clearance for the body or band back 
when a cut is being made. 

SIDE CLEARANCE: The difference between 
the dimension of the band back (gauge) and the 
set of the teeth. Side clearance provides running 
room for the band back in the kerf or cut. 
Without side clearance, a band will bind in the 
kerf. 



used for cutting hollow materials, such as pipe 
and tubing, and for other work where there is a 
great deal of variation in thickness. Straight set 
bands are not used to any great extent for metal 
cutting work. 



TEMPER: The degree of hardness of 
the teeth, indicated by the letters A and 
B, temper A being the harder. Temper A bands 
are used for practically all bandsaw metal cutting 
work. 



File Bands 

A file band consists of a long steel strip upon 
which are mounted a number of file segments that 
can be flexed around the band wheels and still 
present a straight line at the point of work. 
Figure 5-10 illustrates the file band flexing 
principle and shows the construction of a file 



A -FILE SEGMENT 
B-BACK BAND 
C- TAIL GATE 
D- SPACER 




SEGMENTS 
LOCKED IN 
ALIGNMENT 



o t > o 



GATE CLIP 



<=o 



o o 



TAIL GATE 




ENDS 

OF 
BAND 



BACK 
.XBAND 




28.41X 



Figure 5-10. File band flexing principle and construction. 



5-7 



band. The parts ot a rue band and tneir functions 
are described below: 

FILE SEGMENT: A section of the cutting 
face of a file band. The individual segments are 
attached to the file band with rivets. 

BACK BAND: The long steel strip or loop on 
which the file segments are mounted. Do not 
confuse this term with BAND BACK, which 
refers to a part of a saw band. 

GATE CLIP: A steel strip at the leading end 
of the back band a part of an adapter for joining 
the back band ends to form the file band loop. 

TAIL GATE: A steel strip at the other end 
of the back band. This is the other half of the 
adapter for joining the back band ends to form 
the file band loop. 

SPACER: A small steel strip inserted between 
the file segment and the surface of the back band. 
There are as many spacers as there are file 
segments in each file band. 

Polishing Bands 

Abrasive coated fabric bands are used for 
grinding and polishing operations in a band tool 
machine. They are mounted in the same way as 
saw and file bands. Figure 5-1 1 shows a polishing 
band. Figure 5-12 shows a backup support strip 




28.43X 

Figure 5-12. Installing a backup support strip for polishing 
band. 



being installed, before the polishing band is 
installed. 




28.42X 



Figure 5-11. Polishing band. 



Band Tool Guides 

SAW BAND GUIDES: The upper and lower 
guides keep the saw band in its normal track when 
work pressure is applied to the saw. The lower 
guide is in a fixed position under the work table, 
and the upper guide is attached to a vertically 
adjustable arm above the table which permits 
raising or lowering the guide to suit the height of 
work. To obtain adequate support for the band 
and yet not interfere with the sawing operation, 
place the upper guide so that it will clear the top 
of the workpiece by 1/8 to 3/8 of an inch. 
Figure 5-13 shows the two principal types of saw 
band guides: the insert type and the roller type. 
Note in both types the antifriction bearing 
surface for the band's relatively thin back edge. 
This feature allows the necessary work pressure 
to be placed on the saw without causing serious 
rubbing and wear. Be sure to lubricate the 



5-8 




A. INSERT 
TYPE 




B. ROLLER 
TYPE 



28.44X 



Figure 5-13. Saw band guides. 



bearings of the guide rollers according to the 
manufacturer's recommendations. 

FILE BAND AND POLISHING BAND 
GUIDES: For band filing operations, the regular 
saw band guide is replaced with a flat, smooth- 
surface metal backup support strip, as shown in 
figure 5-14, which prevents sagging of the file 
band at the point of work. A similar support is 
used for a polishing band. This support has a 
graphite-impregnated fabric face that prevents 
undue wear on the back of the polishing band, 
which also is fabric. 




28.45X 



Figure 5-14. File band guide. 



SELECTION OF SAW BANDS, 
SPEEDS AND FEEDS 

Saw bands are available in widths ranging 
from 1/16 to 1 inch; in various even-numbered 
pitches from 6 to 32; and in three gauges 0.025, 
0.032, and 0.035 inch. The gauge of saw band that 
can be used in any particular machine depends 
on the size of the band wheels. A thick saw band 
cannot be successfully used on a machine that has 
small diameter bandwheels; therefore, only one 
or two gauges of blades may be available for some 
machines. Generally, only temper A, raker set, 
and wave set bands are used for metal cutting 
work. Another variable feature of saw bands is 
that they are furnished in ready made loops of 
the correct length for some machines, while for 
others they come in coils of 100 feet or more from 
which a length must be cut and formed into a 
band loop by butt welding the ends together in 
a special machine. The process of joining the ends 
and installing bands will be described later in this 
chapter. 

Band tool machines have a multitude of band 
speeds, ranging from about 50 feet per minute to 
about 1500 feet per minute. Most of these 
machines are equipped with a hydraulic feed 
which provides three feeding pressures: low, 
medium, and heavy. 

Success in your precision sawing with a metal 
cutting bandsaw depends to a large extent on your 
selecting the correct saw blade or band, running 



5-9 



the saw band at the correct speed, and feeding 
the work to the saw at the correct rate. Many band 
tool machines have a JOB SELECTOR similar 
to the one shown in figure 5-15, which indicates 
the kind of saw band you should use, the speed 
at which to operate the machine, and the power 
feed pressure to use to cut various materials. 

Not all bandsaws have a job selector. You 
must know something about selecting the correct 
saw bands, speeds, and feeds to operate a band- 
saw successfully. Table 5-1 gives you some of 
that information. Although this table does not 
cover all types and thicknesses of metals nor 
recommended feed pressure, it provides a basis 
on which you can build, using your own 
experience. 

Tooth Pitch 

Tooth pitch is the primary consideration in 
selecting a saw band for any cutting job. For 
cutting thin materials, the pitch should be fine 
enough so that at least two teeth are in contact 
with the work; fewer than two will tend to cause 
the teeth to snag and tear loose from the band. 




For cutting thick material, you should not have 
too many teeth in contact with the work, because 
as you increase the number of teeth in contact, 
you must increase the feed pressure in order to 
force the teeth into the material. 

Excessive feed pressure puts severe strain on 
the band and the band guides. It also causes the 
band to wander sideways which results in off-line 
cutting. Other points to consider in selecting a saw 
band of proper pitch for a particular cutting job 
are the composition of the material to be cut, its 
hardness, and its toughness. Table 5-1 is a saw 
band pitch and velocity selection chart showing 
the pitch of saw band to use for cutting many 
commonly used metals. 

Band Width and Gauge 

The general rule is to use the widest and 
thickest saw band that can do the job successfully. 
For example, you should use a band of maximum 
width and thickness (if bands of different 
thickness are available) when the job calls for only 
straight cuts. On the other hand, when a layout 
requires radius cuts (curved cuts), the band you 
select must be capable of following the sharpest 
curve involved. Thus for curved work, select the 
widest band that will negotiate the smallest radius 
required. The saw band width selection guides, 
shown in figure 5-16, give the radius of the 



WIDTH OF 
SAW BAND 


MINIMUM 
RADII CUT 


1/16' 


SQ. 


3/'-- 1 


1/16" 


1/8 


1/8" 


3/le" 


S/16" 


1/4" 


s/a" 


3/8" 


1-7/16' 


1/2' 


2-1/Z" 


5/8- 


3-3/4" 


3/4" 


5-7/16" 


1* 


7-1/4" 




>/. '/i- vf 'A' w v>'W w 



28.46X 



Figure 5-15. Job selector. 



28.47X 
Figure 5-16. Saw band width selection guides. 



5-10 



MATERIAL 



SAW PITCH 



Work Thickness 



Over 
2" 



SAW VELOCITY 



Work Thickness 



Over 



FERROUS METALS 

Carbon Steel #1010-tl095*. 14 

Free Machining #X1112-#1340*. . . 14 

Nickel Chromium #2115-#3415* . . 14 

Molybdenum #4023 -#4820.*. 14 

Chromium #5120-#52100 * 14 

Tungsten #7620-#71360 * 14 

Silicon Manganese #9255-#9260 14 
* (SAE numbers) 

Armor Plate 14 

Graphitic Steel 14 

High Speed Steel 14 

Stainless Steel 12 

Angle Iron 14 

Pipe 14 

I Beams & Channels 14 

Tubing (Thinwall) 14 

Cast Steels 14 

Cast Iron 12 

NON-FERROUS METALS 

Aluminum (All Types) 8 

Brass 8 

Bronze (Cast) 10 

Bronze (Rolled) 12 

Beryllium Copper 10 

Copper 10 

Magnesium 8 

Kirksite 10 

Monel Metal 10 

Zinc 8 

NON-METALS 

Bakelite 10 

Carbon 10 

Plastics (All Types) 12 

Wood 8 



10 
8 

10 
10 
10 
10 

10 



12 
12 
10 
10 
14 
12 
14 
14 
12 
10 



6 
8 
8 

10 
8 
8 
8 
8 
8 
8 



8 
8 
8 
8 



6-8 
6-8 
6-8 
6-8 
8 
6-8 

6-8 



6-8 

6-8 

8 

8 

10 
8 

10 

14 

8 

8 



6-8 
8 
8 

6-8 
6-8 
6-8 
6-8 
6-8 
6-8 
6-8 



6-8 

6-8 

8 

6-8 



175 
250 
100 
125 
100 
85 

100 



100 
150 
100 
60 
190 
250 
250 
250 
150 
200 



250 
250 
175 
175 
175 
250 
250 
200 
100 
250 



250 
250 
250 
250 



150 

200 

85 

100 

75 

60 

75 



75 
125 

75 

50 
175 
225 
200 
200 

75 
185 



250 
250 
125 
125 
150 
225 
250 
175 
75 
225 



250 
250 
250 
250 



125 
150 
60 
75 
50 
50 

50 



50 

75 

50 

40 

150 

185 

175 

200 

50 

160 



250 

250 

50 

75 

125 

225 

250 

150 

50 

200 



250 
250 
250 
250 



5-11 



sharpest curve that can be cut with a particular 
width saw band. Note that the job selector 
illustrated in figure 5-15 contains a saw band radii 
cutting diagram similar to the one shown in figure 
5-16. 



Band Speeds 

The rate at which the saw band travels in feet 
per minute from wheel to wheel is the saw band 
velocity. Saw band velocity has considerable 
effect upon both the smoothness of the cut 
surfaces and the life of the band. The higher the 
band velocity, the smoother the cut; however, heat 
generated at the cutting point increases as band 
velocity increases. Too high a band velocity causes 
overheating and failure of the saw teeth. The band 
velocities given in Table 5-1 are based on 
manufacturers' recommendations, which in turn 
are based on data obtained from saw life tests and 
cutting experiments under various conditions. If 
you follow the recommendations given, you will 
be assured of the best band performance and 
maximum band life. 

Adjustment of the machine to obtain the 
proper band velocity cannot be covered in detail 
here because speed change is done by different 
methods on different models of machines. 
Consult the manufacturer's technical manual for 
your particular machine and learn how to set up 
the various speeds available. 



Feeds 

Though manual feeding of the work to the saw 
is satisfactory for cutting metals up to 1 inch thick, 
power feeding generally provides better results and 
will be much safer for the operator. Regardless 
of whether power or manual feed is used, it is 
important not to crowd the saw because the band 
will tend to bend and twist. However, feed 
pressure must not be so light that the teeth slip 
across the material instead of cutting through 
because this rapidly dulls the teeth. The job 
selector, shown in figure 5-15, shows the correct 
feed pressures for cutting any of the materials 
listed on the outer ring of the dial. In the absence 
of a job selector, you can use table 5-2 as a guide 
for selecting feed pressures for hard, medium 
hard, and soft metals. 

The power feed controls vary with different 
makes of handsaws and even with different 
models of the same make; therefore, no 
description of the physical arrangement of the 
power feed controls will be given here. Consult 
the manufacturer's technical manual and study 
the particular machine to learn its power feed 
arrangement and control. 



SIZING, SPLICING, 

AND INSTALLING BANDS 

Most contour cutting type handsaws are 
provided with a buttwelder-grinder combination 



Table 5-2. Feed Pressures* for Hard, Medium Hard, and Soft Metal 



Material 


Work thickness 


0-1/4" 


1/4-1/2" 


1/2-1" 


1-3" 


Over 3" 


Tool Steel 


M 
M 
L 
L 
L 
L 
L 


M 
M 
M 
M 
L 
L 
L 


H 
M 
H 
H 
M 
M 
M 


H 
H 
H 
H 
H 
M 
M 


H 
H 
H 
H 
H 
M 
M 


Cast iron 


Mild steel 


Nickel-copper .... 
Copper-nickel .... 
Zinc 


Lead 





L-light, M-medium, H-heavy. 



5-12 



makes inside cutting possible, since the saw 
band loop can be parted and rejoined after 
having been threaded through a starting hole in 
the work. 

The following sections describe how to 
determine the length of the band, how to join the 
ends in the butt welder, and how to install a band 
tool in the machine. 



Band Length 

You can quickly determine the correct saw 
band length for any two-wheeled bandsaw by 
measuring the distance from the center of 
one wheel to the center of the other wheel, 
multiplying by 2, and adding the circumference 
of one wheel. 




Figure 5-17. Butt welder-grinder unit. 



adjust the upper wheel so that it is approximately 
halfway between the upper and lower limits of its 
vertical travel. This allows for taking up any band 
stretch resulting from operation. 



Band Splicing 

Figure 5-17 shows band ends being joined by 
using a butt welder. The procedure for joining is 
as follows: 

1 . Grind both ends of the band until they are 
square with the band back edge. If you do 
not do this carefully, the weld may not go 
completely across the ends of the band and, 
as a result, the weld will not withstand the 
pressure of the cut when it is used. One easy 
method to ensure that the ends of the band 
will go together perfectly is to twist one end 
180 degrees and then place the band ends 
on top of each other. This will provide a 
set of teeth and a band back edge on both 
sides of the stacked ends. Ensure that the 
band back edge and the teeth are in a 
straight line on both sides. Carefully touch 
the tips of the ends of the band to the face 
of the grinding wheel and lightly grind until 
both ends have been ground completely 
across. Release the ends of the band so that 
they assume their normal position. Lay the 
back edge of the band on a flat surface and 
bring the ends together. If you did the 
grinding correctly, the ends will meet 
perfectly. 



2. Set the controls of the butt welder to the 
weld position and adjust the adjusting lever 
according to the width of band to be 
welded. The various models of butt welders 
that are found in many machine shops 
differ in the number of controls that must 
be set and the method of setting them. 
Most models have a lever that must be 
placed in the weld position so that the 
stationary and the movable clamping jaws 
28.4SX are separated the correct distance. Some 

models have a resistance setting control 



5-13 



which is set according to the width of the 
band, while other models have a jaw 
pressure control knob that is also set 
according to band width. Read the 
manufacturer's instruction manual care- 
fully before attempting welding. 

3 . Place the ends of the band in the jaws with 
the teeth of the band facing away from the 
welder. Push the back edge of the band 
firmly back toward the flat surfaces behind 
the clamping jaws to ensure proper align- 
ment. Position the ends of the band so that 
they touch each other and are located in 
the center of the jaw opening. Some models 
of butt welders have interchangeable inserts 
for the clamping jaws to permit welding 
bands of different widths. This is done so 
that the teeth of the band are not damaged 
when the jaws are clamped tight. 

4. You are now ready to weld the band. Some 
welders require that the weld button be 
fully depressed and held until the welding 
is complete, while other welders required 
only that the button be fully depressed and 
then quickly released. There will be a 
shower of sparks from the welding action. 
Be sure you are wearing either safety glasses 
or a face shield before welding and then 
stand back from the welder when you push 
the button. 

5. When the welding is complete, release 
the jaw clamps and remove the band from 
the welder. Inspect the band to be sure it 
is straight and welded completely across. 
Do not bend or flex the band at this- time 
to test the weld. The welding process 
has made the weld and the area near it hard 
and brittle and breakage will probably 
occur. 

6. Place the lever that controls movement 
of the jaws in the anneal position. This 
should separate the jaws again. Set the 
control that regulates the anneal tempera- 
ture to the setting for the width of the 
band. 

7. Place the band in the clamping jaws with 
the teeth toward the welder and the welded 
section in the center of the jaw opening. 
Close the jaws. 



8. The band is ready to be annealed. Push 
and then quickly release the anneal button 
repeatedly until the welded area becomes 
a dull cherry red. (Do NOT push and hold 
the anneal button. This will overheat and 
damage the band.) After the proper 
temperature is reached, push the anneal 
button and release it with increasingly 
longer intervals between the push cycle to 
allow the band to cool slowly. 

9. The metal buildup resulting from the weld 
must be ground off. Using the attached 
grinding wheel, remove the weld buildup 
from both sides and the back of the band 
until the band fits snugly into the correct 
slot on the saw band thickness gauge 
mounted on the welder. Do this grinding 
carefully to prevent looseness or binding 
between the saw guides and the band. Be 
careful not to grind on the teeth of the 
band. 

10. Repeat the procedure for annealing in step 
8 after grinding the blade. 

11. The welding process is complete. To test 
your weld, hold the band with both hands 
and form a radius in the band slightly 
smaller than the smallest wheel on the 
bandsaw by bringing your hands together. 
Move your hands up and down in 
opposite directions and observe the 
welded area as it rolls around the radius 
that you formed. 



Installing Bands 

Insert saw band or tool guides of the correct 
size for the band you are going to install. Adjust 
the upper band wheel for a height that will allow 
you to easily loop the band around the wheels. 
Then place one end of the loop over the upper 
band wheel and the other end of the loop around 
the lower band wheel, being sure that the teeth 
are pointing downward on the cutting side of the 
band loop and that the band is properly located 
in the guides. Place a slight tension on the band 
by turning the upper wheel takeup hand wheel 
and revolve the upper band wheel by hand until 
the band has found its tracking position. If 
the band does not track on the center of the 
crowns of the wheels, use the upper wheel tilt 



. . , 

band guide rollers or inserts so that you have a 
total clearance of 0.001 to 0.002 inch between the 
sides of the band back and the guide rollers or 
inserts, and a slight contact between the back edge 
of the band back and the backup bearings of the 
guides. When you have set the band guide 
clearance, increase the band tension. The amount 
of tension to put on the band depends on the 
width and gauge of the band. A narrow, thin band 
will not stand as much tension as a wider or 
thicker band. Too much tension will cause the 
saw to break; insufficient tension will cause 
the saw to run off the cutting line. The best 
way to obtain the proper tension is to start 
with a moderate tension; if the saw tends to 
run off the line when cutting, increase the 
tension slightly. 



SAWING OPERATIONS 

As previously mentioned, the types of sawing 
operations possible with a band tool machine are 
straight, angular, contour, inside, and disk 
cutting. The procedures for each of these cutting 
operations are described in the following 
paragraphs; but first, let us consider the general 
rules applicable to all sawing operations. 




28.49X 



Figure 5-18. Upper wheel tilt adjustment. 



adjust me table, it necessary, to suit the 
angle of the cut. 

Use the proper blade and speed for each 
cutting operation. This ensures not only 
the fastest and most accurate work but also 
longer saw life. 

Always be sure the band guide inserts are 
the correct size for the width of the band 
installed and that they are properly 
adjusted. 

Before starting the machine, adjust the 
height of the upper band guide so that it 
will clear the work from 1/8 to 3/8 inch. 
The closer the guide is to the work, the 
greater the accuracy. 

When starting a cut, feed the work to the 
saw gradually. After the saw has started 
the kerf, increase the feed slowly to the 
recommended pressure. Do not make a 
sudden change in feed pressure because 
such a change may cause the band to 
break. 



Be sure the saw band and guides are 
properly lubricated. 

Use lubricants and cutting coolants as 
recommended by the manufacturer of your 
machine. 



Straight Cuts with Power Feed 

1. Change band guides as necessary. Select 
and install the proper band for the job and 
adjust the band guides. 

2. Place the workpiece on the table of the 
machine and center the work in the work 
jaw. 

3. Loop the feed chain around the work 
jaw, the chain roller guides, and the 



5-15 



left-right guide sprocket, as shown in 
figure 5-19. 

4. Determine the proper band speed and set 
the machine speed accordingly. 

5. Start the machine and feed the work to the 
saw in the manner described in the general 
rules of operation given in the preceding 
section. Use the left-right control for 
guiding the work along the layout line. 

Angular Cutting 

Angular or bevel cuts on flat pieces are made 
in the same way as straight cuts except that the 
table is tilted to the desired angle of the cut as 
shown in figure 5-20. 

Contour Cutting 

Contour cutting, that is, following straight, 
angle, and curved layout lines, can be done 




28.51X 



Figure 5-20. Angular cutting. 



LEFT-RIGHT GUIDE SPROCKET 



LEFT-RIGHT CONTROL KNOB 




28. SOX 



Figure 5-19. Work jaw and feed chain adjustment. 



for guiding the work along the layout line when 
power feed is used. A fingertip control for 
actuating the sprocket is located at the edge of 
the work table. If there are square corners in the 
layout, drill a hole adjacent to each corner; this 
will permit the use of a wider band, greater feed 
pressure, and faster cutting. Figure 5-21 shows the 
placement of corner holes on a contour cutting 
layout. 




28.52X 

Figure 5-21. Sharp radii cutting eliminated by drilling 
corner holes. 



To make an inside cut, drill a starting hole 
slightly larger in diameter than the width of the 
band you are going to use. Remove the band from 
the machine. Shear the band; slip one end through 
the hole, and then splice the band. When the band 
has been spliced and reinstalled, the machine is 
ready for making the inside cut as illustrated in 
figure 5-22. 

Disk Cutting 

Disk cutting can be done either offhand by 
laying out the circle on the workpiece and follow- 
ing the layout circle or by using a disk cutting 
attachment which automatically guides the work 
so that a perfect circle is cut. Figure 5-23 shows 
a disk cutting attachment in use. The device 
consists of a radius arm, a movable pivot point, 
and a suitable clamp for attaching the assembly 
to the saw guidepost. To cut a disk using this 
device, lay out the circle and punch a center point. 
Clamp the radius arm to the guidepost. Position 
the workpiece (fig. 5-23) so that the saw teeth are 
tangent to the scribed circle. Adjust the pivot 
point radially and vertically so that it seats in the 
center-punch mark; then clamp the pivot point 
securely. Then rotate the work around the pivot 
point to cut the disk. 

Filing and Polishing 

In filing and polish finishing, the work is 
manually fed and guided to the band. Proper 





28.53X 



Figure 5-22. Inside cutting. 



28.54X 



Figure 5-23. Disk-cutting attachment. 



5-17 



installation of the guides and backup support 
strips is very important if good results are to be 
obtained. A guide fence similar to the one shown 
in figure 5-24 is very helpful when working to 
close tolerances. Be sure to wear goggles or an 
eye protection shield when filing and polishing, 
and above all, be careful of your fingers. For 
proper band speeds and work pressures, consult 
the manufacturer's technical manual for the 
machine you are using. 



DRILLING MACHINES 
AND DRILLS 

Although drilling machines or drill presses are 
commonly used by untrained personnel, you 
cannot assume that operating these machines 
proficiently is simply a matter of inserting the 
proper size drill and starting the machine. As a 
Machinery Repairman, you will be required to 
perform drilling operations with a great degree 
of accuracy. It is therefore necessary for you to 
be well acquainted with the types of machines and 
the methods and techniques of operation of drill 
presses and drills found in Navy machine shops. 

DRILLING MACHINE 
SAFETY PRECAUTIONS 

Because of the widespread use of the drill press 
by such a diverse group of people with different 
training and experience backgrounds, some 




28.55X 



Figure 5-24. Polish finishing. 



unsafe operating practices have become rather 
routine in spite of the possibility of serious injury. 
The basic safety precautions for the use of a drill 
press are listed below: 

Always wear safety glasses or a face shield 
when you operate a drill press. 

Keep loose clothing clear of rotating parts. 

NEVER attempt to hold a piece being 
drilled in your hand. Use a vise, hold-down 
bolts or other suitable clamping device. 

Check the twist drill to ensure that it is 
properly ground and is not damaged or 
bent. 

Make sure that the cutting tool is held 
tightly in the drill press spindle. 

Use the correct feeds and speeds. 

When feeding by hand, take care to 
prevent the drill from digging in and taking 
an uncontrolled depth of cut. 

Do NOT remove chips by hand. Use a 
brush. 



TYPES OF MACHINES 

The two types of drilling machines or drill 
presses common to the Navy machine shop are 
the upright drill press and the radial drill 
press. These machines have similar operating 
characteristics but differ in that the radial drill 
provides for positioning the drilling head rather 
than the workpiece. 

Upright drill presses discussed in this section 
will be the general purpose, the heavy duty, and 
the sensitive drill presses. One or more of these 
types will be found on practically all ships. They 
are classified primarily by the size of drill that can 
be used, and by the size of the work that can be 
set up. 

The GENERAL PURPOSE DRILL PRESS 
(ROUND COLUMN), shown in figure 5-25, is 
perhaps the most common upright type of 
machine and has flexibility in operational 
characteristics. The basic components of this 
machine are shown in the illustration. 



SPEED 

CHANGE 

GEARS 



DRIVE 
MECHANISM 



ARM, 




SPINDLE 
HEAD 



SPINDLE 



WORKTABLE 



BASE 



Figure 5-25. General purpose drill press. 



11.9 



The BASE has a machined surface with T-slots 
for heavy or bulky work. 

The COLUMN supports the work table, the 
drive mechanism and the spindle head. 

The WORK TABLE and ARM can be 

swiveled around the column and can be moved 
up or down to adjust for height. In addition, the 
work table may be rotated 360 about its own 
center. 

The SPINDLE HEAD guides and supports 
the spindle and can be adjusted vertically to 
provide maximum support near the spindle 
socket. 

The SPINDLE is a splined shaft with a Morse 
taper socket for holding the drill. The spline 
permits vertical movement of the spindle while it 
is rotating. 



HEAVY DUTY DRILL PRESSES (BOX 
COLUMNS) are normally used in drilling large 
holes. They differ from the general purpose drill 
presses in that the work table moves only 
vertically. The work table is firmly gibbed to 
vertical ways or tracks on the front of the column 
and is further supported by a heavy adjusting 
screw from the base to the bottom of the table. 
As the table can be moved only vertically, it is 
necessary to position the work for each hole. 

The SENSITIVE DRILL PRESS shown in 
figure 5-26 is used for drilling small holes in work 
under conditions which make it necessary for the 
operator to "feel" what the cutting tool is doing. 
The tool is fed into the work by a very simple 
device a lever, a pinion and shaft, and a rack 
which engages the pinion. These drills are nearly 
always belt-driven because the vibration caused 



FEED LEVER 




11.10 



Figure 5-26. Sensitive drill press. 



5-19 



by gearing would be undesirable. Sensitive drill 
presses are used in drilling holes less than one- 
half inch in diameter. The high-speed range of 
these machines and the holding devices used make 
them unsuitable for heavy work. 

The RADIAL DRILL PRESS, shown in 
figure 5-27, has a spindle head on an arm that can 
be rotated axially on the column. The spindle head 
may be traversed horizontally along the ways of 
the arm, and the arm may be moved vertically on 
the column. This machine is especially useful 
when the workpiece is bulky or heavy or when 
many holes can be drilled with one setup. The arm 
and spindle are designed so that the drill can be 
positioned easily over the layout of the workpiece. 

Some operational features that are common 
to most drilling machines are: (1) high- and low- 
speed ranges provided from either a two-speed 
drive motor or a low-speed drive gear; (2) a 
reversing mechanism for changing the direction 
of rotation of the spindle by either a reversible 
motor or a reversing gear in the drive gear train; 
(3) automatic feed mechanisms which are driven 
from the spindle and feed the cutting tool at a 
selected rate per revolution of the spindle; (4) 
depth setting devices which permit the operator 



to preset the required depth of penetration o 
cutting tool; and (5) coolant systems to prc 
lubrication and coolant to the cutting tool 

On other machines the control levers m* 
placed in different positions; however, they i 
the same purposes as those shown. In usini 
locking clamps to lock or "dog down" the i 
or head of a drill after it is positioned ove 
work, make sure that the locking action doe 
cause the drill or work to move slightly o\ 
position. 



TWIST DRILL 

The twist drill is the tool generally usec 
drilling holes in metal. This drill is formed e 
by forging and twisting grooves in a flat str: 
steel or by milling a cylindrical piece of st 

In figure 5-28 you see the principal par 
a twist drill: the BODY, the SHANK, anc 
POINT. The portion of the LAND behinc 
MARGIN is relieved to provide BC 
CLEARANCE. The body clearance assisi 
reducing friction during drilling. The LIP i; 
cutting edge, and on the CONE of the drill i 



COLUMN 



ARM ELEVATING SCREW 



COMBINATION ARM ELEVATING 
AND LOCKING LEVER 



COLUMN LOCKING 
LEVER 




SPINDLE HEAD 



FEED CHANGE LEVER 



SPINDLE SOCKET 



Figure 5-27. Radial drill press. 



CUTTING EDGE 



FLUTE 




SHANK < 



TANG 



Figure 5-28. The parts of a twist drill. 



44.20 



area called the LIP CLEARANCE. DEAD 

CENTER is the sharp edge located at the tip end 
of the drill. It is formed by the intersection of the 
cone-shaped surfaces of the point and should 
always be in the exact center of the axis of the 
drill. Do not confuse the point of the drill with 
the dead center. The point is the entire cone- 
shaped surface at the cutting end of the drill. The 
WEB of the drill is the metal column which 
separates the flutes. It runs the entire length of 
the body between the flutes and gradually 
increases in thickness toward the shank, giving 
additional rigidity to the drill. 

The TANG is found only on tapered-shank 
tools. It fits into a slot in the socket or spindle 



remove the drill from the socket with the aid of 
a drill drift. (NEVER use a file or screwdriver to 
do this job.) 

The SHANK is the part of the drill which 
fits into the socket, spindle, or chuck of the 
drill press. The types of shanks that are most 
often found in Navy machine shops are the 
Morse taper shank, shown in figures 5-28 and 
5-29A and the straight shank, shown in figures 
5-29B and 5-29C. 

Twist drills are made from several different 
materials. Drills made from high-carbon steel 
are available; however, the low cutting speed 
required to keep this type of drill from becoming 
permanently dull limits their use considerably. 
Most of the twist drills that you will use are made 
from high-speed steel and will have two flutes (fig. 
5-28). 

Core drills (fig. 5-29 A) have three or more 
flutes and are used to enlarge a cast or previously 
drilled hole. Core drills are more efficient and 
more accurate when used to enlarge a hole than 



Figure 5-29. Twist drills: A. Three-fluted core drill; 

B. Carbide tipped drill with two helical flutes; 

C. Carbide tipped die drill with two flutes parallel to the 
drill axis. 



5-21 



the standard two-fluted drill. Core drills are made 
from high-speed steel. 

A carbide-tipped drill (fig. 5-29B), which is 
similar in appearance to a standard two-fluted 
drill with carbide inserts mounted along the lip 
or cutting edge, is used for drilling nonferrous 
metals, cast iron, and cast steel at high speeds. 
These drills are not designed for drilling steel and 
alloy metals. 

A carbide-tipped die drill, or spade drill as it 
is often called (fig. 5-29C), has two flutes that run 
parallel to the axis of the drill as opposed to the 
helical flutes of the standard two-fluted drill. This 
drill can be used to drill holes in hardened steel. 

A standard two-fluted drill made from cobalt 
high-speed steel is superior in cutting efficiency 
and wear resistance to the high-speed steel drill 
and is used at a cutting speed between the speed 
recommended for a high-speed steel drill and a 
carbide-tipped drill. 

A solid carbide drill with two helical flutes is 
also available and can be used to drill holes in hard 
and abrasive metal where no sudden impact will 
be applied to the drill. 

Drill sizes are indicated in three ways: by 
measurement, letter, and number. The nominal 
measurements range from 1/16 to 4 inches or 
larger, in 1/64-inch steps. The letter sizes run from 
"A" to "Z" (0.234 to 0.413 inch). The number 
sizes run from No. 80 to No. 1 (0.0135 to 0.228 
inch). 

Before putting a drill away, wipe it clean and 
then give it a light coating of oil. Do not leave 
drills in a place where they may be dropped or 
where heavy objects may fall on them. Do not 
place drills where they will rub against each other. 



DRILLING OPERATIONS 

Using the drill press is one of the first skills 
you will learn as a Machinery Repairman. 
Although a drill press is relatively simpler to 
operate and understand than other machine tools 
in the shop, the requirements for accuracy and 
efficiency in its use are no less strict. To achieve 
skill in drilling operations, you must have a 
knowledge of feeds and speeds, how the work is 
held, and how to ensure accuracy. 



Speeds, Feeds, and Coolants 

The cutting speed of a drill is expressed in feet 
per minute (fpm). This speed is computed by 
multiplying the circumference of the drill (in 
inches) by the revolutions per minute (rpm) of 
the drill. The result is then divided by 12. 
For example, a 1/2-inch drill, which has a 
circumference of approximately 11/2 inches, 
turned at 100 rpm has a surface speed of 
150 inches per minute. To obtain fpm, divide this 
figure by 12 which results in a cutting speed of 
approximately 12 1/2 feet per minute. 

The correct cutting speed for a job depends 
on many variable factors. The machinability of 
a metal, any heat treatment process such as 
hardening, tempering, or normalizing, the type 
of drill used, the type and size of the drilling 
machine, the rigidity of the setup, the finish and 
accuracy required, and whether or not a cutting 
fluid is used are the main factors that you must 
consider when selecting a cutting speed for 
drilling. The following cutting speeds are 
recommended for high-speed steel twist drills. 
Carbon steel drills should be run at one-half these 
speeds, while carbide may be run at two to three 
times these speeds. As you gain experience in 
using twist drills, you will be able to vary the 
speeds to suit the job you are doing. 

Low carbon steel 80-1 10 fpm 

Medium carbon steel 70- 80 fpm 

Alloy steel 50-70 fpm 

Corrosion-resistant 

steel (stainless) 30-40 fpm 

Brass 200-300 fpm 

Bronze 200-300 fpm 

Monel 40-50 fpm 

Aluminum 200-300 fpm 

Cast iron 70-150 fpm 

The speed of the drill press is given in rpm. 
Tables giving the proper rpm at which to run a 
drill press for a particular metal are usually 
available in the machine shop, or they may be 
found in machinists' handbooks. A formula may 
be used to determine the rpm required to give a 
specific rate of speed in fpm for a specific size 
drill. For example, if you wish to drill a 



5-22 






TI X D 



50 x 12 
3. 1416 x 1 



600 



3.1416 



= 190 



where 



fpm = required speed in feet per minute 
7r = 3.1416 
12 = constant 
D = diameter of drill in inches 

The feed of a drill is the rate of penetration 
into the work for each revolution. Feed is 
expressed in thousandths of an inch per 
revolution. In general, the larger the drill, the 
heavier the feed that may be used. Always 
decrease feed pressure as the drill breaks through 
the bottom of the work to prevent drill breakage 
and rough edges. The rate of feed depends on the 
size of the drill, the material being drilled, and 
the rigidity of the setup. 

Use the following feed rates, given in 
thousandths of an inch per revolution (ipr), as a 
general guide until your experience allows you to 
determine the most efficient feed rate for each 
different job. 



Drill Diameter 
No. 80 to 1/8 inch 
1/8 inch to 1/4 inch 
1/4 inch to 1/2 inch 
1/2 inch to 1 inch 
Greater than 1 inch 



IPR 

0.001-0.002 
0.002-0.004 
0.004-0.007 
0.007-0.015 
0.015-0.025 



Use the lower feed rate given for each range of 
drill sizes for the harder materials such as tool 
steel, corrosion-resistant steel and alloy steel. Use 
the higher feed rate for brass, bronze, aluminum, 
and other soft metals. 



corrosion-resistant steel and certain nonferrous 
metals such as Monel. For most drilling opera- 
tions, you can use soluble oil. You may drill 
aluminum, brass, cast iron, bronze and similarly 
soft metals dry unless you use a high drilling 
speed and feed. Use mineral-lard oil for the 
exceptionally hard metals. 

Holding the Work 

Before drilling, be sure your work is well 
clamped down. On a sensitive drill press you will 
probably have to use a drill vise and center the 
work by hand. Because the work done on this drill 
press is comparatively light, the weight of the vise 
is sufficient to hold the work in place. 

The larger drill presses have slotted tables to 
which work of considerable weight can be bolted 
or clamped. T-bolts, which fit into the T-slots on 
the table, are used for securing the work. Various 
types of clamping straps, shown in figure 5-30, 
also can be used. (Clamping straps are also 
identified as clamps or dogs.) The U-strap is the 
most convenient for many setups because it has 
a larger range of adjustment. 

It is often necessary to use tools such as 
steel parallels, V-blocks, and angle plates for 
supporting and holding the work. Steel parallels 




GOOSENECK STRAP 



U-STRAP 



11.15 



Figure 5-30. Common types of clamping straps. 



5-23 



are used to elevate the work above the table so 
you can better see the progress of the drill. 
V-blocks are used for supporting round stock, and 
angle plates are used to support work where a hole 
is to be drilled at an angle to another surface. 
Some examples of setups are shown in figure 5-31. 



Drilling Hints 

To ensure accuracy in drilling, position the 
work accurately under the drill, and use the proper 
techniques to prevent the drill from starting off 
center or from moving out of alignment during 
the cut. Here are some hints that will aid you in 
correctly starting and completing a drilling job. 

1. Before setting up the machine, wipe all 
foreign matter from the spindle and the 
table of the machine. A chip in the spindle 
socket will cause the drill to have a 
wobbling effect which tends to make the 
hole larger than the drill. Foreign matter 
on the work holding device under the 
workpiece tilts it in relation to the spindle, 
causing the hole to be out of alignment. 

2. Center punch the work at the point to be 
drilled. Position the center-punched 
workpiece under the drill. Use a dead 
center inserted in the spindle socket to 
align the center-punch mark on the 
workpiece directly under the axis of the 
spindle. 



ANGLE PLATE 




DRILL PRESS 
TABLE 




3 . Bring the spindle with the inserted center 
down to the center-punch mark and hold 
it in place lightly while fastening the locking 
clamps or dogs. This will prevent slight 
movement of the workpiece, table, or both 
when they are clamped in position. 

4. Insert a center drill (fig. 5-32) in the spindle 
and make a center hole to aid in starting 
the drill. This is not necessary on small 
drills on which the dead center of the drill 
is smaller than the center-punch mark, but 
on large drills it will prevent the drill 
from "walking" away from the center- 
punch mark. This operation is especially 
important in drilling holes on curved 
surfaces. 

5 . Using a drill smaller than the required size 
to make a pilot hole will increase accuracy 
by eliminating the need for the dead center 
oif the finishing drill to do any cutting, 
decreasing the pressure required for feeding 
the finishing drill and decreasing the width 
of cut taken by each drill. In drilling holes 
over 1 inch in diameter, you may need to 
use more than one size of pilot drill to 
increase the size of the hole by steps until 
the finished size is reached. 

6. If the outer corners of the drill (margin) 
appear to be wearing too fast or have a 
burnt look, the drill is going too fast. 

7. If the cutting edges (lips) chip during 
drilling, too much lip clearance has been 
ground into the drill, or you are using too 
heavy a feed rate. 

8. A very small drill will break easily if the 
drill is not going fast enough. 

9. When a hole being drilled is more than 
three or four times the drill diameter in 
depth, back out the drill frequently to clear 
the chips from the flutes. 





Figure 5-31. Work mounted on the table. 



11.16 Figure 5-32.- 



-Combined drill and countersink (center 
drill). 



10. If the drill becomes hot quickly, is difficult 
to feed, squeals when being fed and 
produces a rough finish in the hole, it has 
become dull and requires resharpening. 

11. If the drill has cutting edges of different 
angles or unequal length, the drill will cut 
with only one lip and will wobble in 
operation, resulting in an excessively over- 
sized hole. 

12. If the drill will not penetrate the work, 
insufficient or no lip clearance has been 
ground into the drill. 

13. The majority of drilled holes will be over- 
sized regardless of the care taken to ensure 
a good setup. Generally, you can expect 
the oversize to average an amount equal 
to 0.004 inch times the drill diameter 
plus 0.003 inch. For example, you 
can expect a 1/2-inch drill to produce 
a hole approximately 0.505 in diameter 
([0.004 x 0.500] + 0.003). This amount 
can vary up or down depending on the 
condition of the drilling machine and the 
twist drill. 

Correcting Offcenter Starts 

A drill may start off center because of 
improper center drilling, careless starting of the 
drill, improper grinding of the drill point, or hard 
spots in the metal. To correct this condition, take 
a half-round chisel and cut a groove on the side 
of the hole toward which the center is to be drawn. 
(See fig. 5-33.) The depth of this groove depends 
upon the eccentricity (deviation from center) of 
the partially drilled hole with the hole to be drilled. 
When the groove is drilled out, lift the drill from 
the work and check the hole for concentricity with 



the layout line. Repeat the operation until the edge 
of the hole and the layout line are concentric. 
When you use this method to correct an off 
center condition, be very careful that the cutting 
edge or lip of the drill does not grab in the chisel 
groove. Generally, you should use very light feeds 
until you establish the new center point. (Heavy 
feeds cause a sudden bite in the groove which may 
result in the work being pulled out of the holding 
device, or the drill being broken.) 

Counterboring, Countersinking, 
and Spotfacing 

A counterbore is a drilling tool used in the drill 
press to enlarge portions of previously drilled 
holes to allow the heads of fastening devices to 
be flush with or below the surface of the 
workpiece. The parts of a counterbore that 
distinguish it from a regular drill are a pilot, which 
aligns the tool in the hole to be counterbored, and 
the cutting edge of the counterbore, which is flat 
so that a flat surface is left at the bottom of the 
cut, enabling fastening devices to seat flat against 
the bottom of the counterbored hole. 

Figure 5-34 shows two types of counterbores 
and an example of a counterbored hole. The basic 
difference between the counterbores illustrated is 
that one has a removable pilot and the other does 
not. A conterbore with provisions for a removable 
pilot can be used in counterboring a range of hole 
sizes by simply using the appropriate size pilot. 
The use of the counterbore with a fixed pilot is 
limited to holes of the same dimensions as the 
pilot. 





11.17 
Figure 5-33. Using a half-round chisel to guide a drill to 




J*| 
piL<5r 



TANG TAPER SHANK SETSCREW 



COUNTERBORE 







Countersinks are used for seating flathead 
screws flush with the surface. The basic difference 
between countersinking and counterboring is that 
a countersink makes an angular sided recess, while 
the counterbore forms straight sides. The angular 
point of the countersink acts as a guide to center 
the tool in the hole being countersunk. Figure 5-35 
shows two common types of countersinks. 

Spotfacing is an operation that cleans up the 
surface around a hole so that a fastening device 
can be seated flat on the surface. This operation 
is commonly required on rough surfaces that have 
not been machined and on the circumference of 
concave or convex workpieces. Figure 5-36 shows 
an example of spotfacing and the application of 
spotfacing in using fastening devices. This opera- 
tion is commonly done by using a counterbore. 

Reaming 

In addition to drilling holes, the drill press may 
be used for reaming. For example, when specifica- 
tions call for close tolerances, the hole must be 
drilled slightly undersize and then reamed to the 
exact dimension. Reaming is also done to remove 
burrs in a drilled hole or to enlarge a previously 
used hole for new applications. 

Machine reamers have tapered shanks that fit 
the drilling machine spindle. Be sure not to 
confuse them with hand reamers, which have 
straight shanks. Hand reamers will be ruined if 
they are used in a machine. 

There are many types of reamers, but the ones 
used most extensively are the straight-fluted, 
the taper, and the expansion types. They are 
illustrated in figure 5-37. 



m 





28.59 



Figure 5-35. Countersinks. 



5-X2 HEX. HEAD 
CAP SCREW 



SPOT 
FACE 




COUNTERBORE 



PILOT 

BODY. 
HOLE 



A B 

Figure 5-36. Examples of spotfacing. 




STRAIGHT FLUTED REAMER 



TAPER REAMER 



EXPANSION REAMER 
Figure 5-37. Reamers. 



5.10 



The STRAIGHT-FLUTED REAMER is 

made to remove small portions of metal and to 
cut along the edges to bring a hole to close 
tolerance. Each tooth has a rake angle which is 
comparable to that on a lathe tool. 

The TAPER PIN REAMER has a tapered 
body and is used to smooth and true tapered holes 
and recesses. The taper pin reamer is tapered at 
1/4 inch per foot. 

The EXPANSION REAMER is especially 
useful in enlarging reamed holes by a few 
thousandths of an inch. It has a threaded plug 
in the lower end which expands the reamer to 
various sizes. 

To ream a hole, follow the steps outlined 
below: 

1 . Drill the hole about 1/64 inch less than the 
reamer size. 

2. Substitute the reamer in the drill press 
without removing the work or changing the 
position of the work. 

3. Adjust the machine for the proper spindle 
speed. (Reamers should turn at about one- 
half the speed of the twist drill.) 

4. Use a cutting oil to ream. Use just enough 
pressure to keep the reamer feeding into the 
work; excessive feed may cause the reamer 
to dig in and break. 

5. The starting end of a reamer is slightly 
tapered; always run it all the way through 
the hole. NEVER RUN A REAMER 
BACKWARD because the edges are likely 
to break. 

Tapping 

Special attachments that permit cutting 
internal screw threads with a tap driven by the 
drilling machine spindle can save considerable 
time when a number of identically sized holes 
must be threaded. The attachment is equipped 



5-26 



with a reversing device that automatically changes 
the direction of rotation of the tap when either 
the tap strikes the bottom of the hole or a slight 
upward pressure is applied to the spindle down- 
feed lever. The reversing action takes place 
rapidly, permitting accurate control over the depth 
of the threads being cut. A spiral-fluted tap should 
be used to tap a through hole while a standard 
straight-fluted plug tap can be used in a blind hole. 
A good cutting oil should always be used in 
tapping with a machine. 

DRILLING ANGULAR HOLES 

An angular hole is a hole having a series of 
straight sides of equal length. A square (4-sided), 
a hexagon (6-sided), a pentagon (5 -sided), and an 
octagon (8-sided) are examples of angular holes. 
An angular hole that goes all the way through a 
part can be made easily by using a broach; 
however, a blind hole, one in which the angular 
hole does not go all the way through the part, can- 
not be made with a broach. There are two 
methods available to you for machining a blind 



angular hole. One method, the shaper, will be 
covered later in Chapter 12. The second method, 
drilling the angular hole in a drill press or on a 
lathe, is described briefly in the following 
paragraphs. 

EQUIPMENT 

The equipment required to drill angular holes 
is specialized and is designed to do only this 
particular operation. The machining process, 
known as the WATTS METHOD, was developed 
by the Watts Bros. Tool Works, Incorporated 
and the required equipment is patented and 
manufactured exclusively by that company. A 
brief description of the equipment is included in 
the following paragraphs. A complete description 
of the equipment and its use is available from the 
manufacturer when the equipment is ordered. 

Chuck 

The chuck (fig. 5-3 8 A) used in drilling angular 
holes is of an unusual design in that while it holds 
the drill in a position parallel to the spindle of the 
lathe or drill press and prevents it from revolving, 




FLOATING CHUCK 



B 





GUIDE PLATES 




GUIDE HOLDER 



D 




SLIP BUSHINGS 




SQUARE DRILL 




HEXAGON 
DRILL 



Figure 5-38. Equipment for drilling angular holes. A. Chuck; B. Guide plate; C. Guide holder; D. Slip bushing; E. Angular 

drill. 



it allows the drill to float freely so that the flutes 
can follow the sides of the angular hole in the 
guide plate. The chuck is available with a Morse 
taper shank to fit most lathes and drill presses. 
There are several different sizes of chucks, each 
capable of accepting drills for a given range of 
hole sizes. 

Guide Plates 

The guide plate (fig. 5-3 8B) is the device that 
causes the drill to make an angular hole. The free- 
floating action of the chuck allows the drill to 
randomly follow the straight sides and corners of 
the guide plate as it is fed into the work. Attach 
the guide plate to a guide holder when you use 
a lathe and directly to the work when you use a 
drill press. A separate guide plate is required for 
each different shape and size hole. 

Guide Holder 

The guide holder (fig. 5-38C), as previously 
stated, holds the guide plate and is placed over 
the outside diameter of the work and locked in 
place with a setscrew. The guide holder is used 
when the work is being done in a lathe and is not 
required for drill press operations. 



Slip Bushings 

Prior to actually drilling with the angular hole 
drill, you must drill a normal round hole in the 
center of the location where the angular hole will 
be located. This pilot hole reduces the pressure 
that would otherwise be required to feed the 
angular drill and ensures that the angular drill will 
accurately follow the guide plate. In a lathe, you 
need only drill a hole using the tailstock since it 
and the chuck will automatically center the pilot 
hole. In a drill press, you must devise a method 
to assist you in aligning the pilot hole. A slip 
bushing will do the job quickly and accurately. 
The slip bushing (fig. 5-38D) fits into the guide 
plate and has a center hole which is the correct 
size for the pilot hole of the particular size angular 
hole being drilled. After you have installed the 
bushing, position the correct drill so that it enters 
the hole in the slip bushing and drill the pilot hole. 



Angular Drill 

The angular drills (fig. 5-38E) are straight 
fluted and have one less flute or cutting lip than 
the number of sides in the angular hole they are 
designed to drill. The drills have straight shanks 
with flats machined on them to permit securing 




Figure 5-39. Lathe setup for drilling an angular hole. 



5-28 



them in the floating chuck with setscrews. The 
cutting action of the drill is made by the cutting 
lips or edges on the front of the drill. 



OPERATION 

The procedure for drilling an angular hole is 
similar to that for drilling a normal hole, differing 
only in the preliminary steps required in setting 
the job up. The feeds and speeds for drilling 
angular holes should be slower than those 
recommended for drilling a round hole of the 
same size. Obtain specific recommendations 
concerning feeds and speeds from the informa- 
tion provided by the manufacturer. Use a coolant 
to keep the drill cool and help flush away the 
chips. The following procedures apply when the 
work is being done on a lathe. See figure 5-39 for 
an example of a lathe setup. 

1 . Place the work to be drilled in the lathe 
chuck. The work must have a cylindrical 
outside diameter and the intended location 
of the angular hole must be in the center 
of the work. 

2. Place the guide holder over the outside 
diameter of the work and tighten the 
setscrew. If the bore in the back of the 
guide holder is larger than the diameter of 
the work, make a sleeve to adapt the two 
together. If the part to be drilled is short, 
place it in the guide holder and place the 
guide holder in the chuck. 

3. Drill the pilot hole at this time. The size 
of the pilot hole should be slightly smaller 
than the distance across the flats of the 
angular hole. The manufacturer makes 
specific recommendations on pilot hole 
sizes. 

4. Attach the guide plate to the guide 
holder. 

5. Mount the floating chuck in the lathe 
tailstock spindle and place the drill in the 
chuck. Tighten the setscrews to hold the 
drill securely. 

6. You are now ready to drill the angular 
hole. Do not force the drill into the 
work too rapidly, and use plenty of 
coolant. 



The setup for drilling an angular hole using 
a drill press differs in that instead of using a guide 
holder, clamp the guide plate directly to the work 
and drill the pilot hole by using a slip bushing 
placed in the guide plate to ensure alignment. 
Once you have positioned the work under the drill 
press spindle and have drilled the pilot hole, do 
not move the setup. Any movement will result in 
misalignment between the work and the angular 
drill. 



METAL DISINTEGRATORS 

There are occasions when a broken tap or a 
broken hardened stud cannot be removed by the 
usual removal methods previously covered. To 
remove such a piece without damaging the 
part, use a metal disintegrator. This machine 
disintegrates a hole through the broken tap 
or stud by the use of an electrically charged 
electrode that vibrates as it is fed into the 
work. The part to be disintegrated and the 
mating part that it is screwed into must be 
made from a material that will conduct electricity. 
Figure 5-40 shows a disintegrator removing a 
broken stud. 

You can obtain the specific operating 
procedure for the metal disintegrator from the 
reference material furnished by the manufacturer; 
however, there are several steps involved in 
setting up for a disintegrating job that are 
common to most of the models of disintegrators 
found aboard Navy ships. 

Setting up the part to be disintegrated is the 
first step that you must do. Some disintegrator 
models have a built-in table with the disintegrating 
head mounted above it in a fashion similar to a 
drill press. On a machine such as this, you need 
only bolt the part securely to the table, ensuring 
that the part makes good contact so that an 
electrical ground is provided. Align the tap or 
stud to be removed square with the table so the 
electrode will follow the center of the hole 
correctly. Misalignment could result in the 
electrode leaving the tap or stud and damaging 
the part. Use either a machinist's square laid on 
the table or a dial indicator mounted on the 
disintegrating head to help align the part. If the 
part will not make an electrical ground to the table 
or if the model of machine being used is designed 
as an attachment to be mounted in a drill press 




Figure 5-40. Metal disintegrator removing a broken stud. 



spindle, attach the disintegrator's auxiliary ground 
cable to the part. 

Selection of the correct electrode depends on 
the diameter and length of the part to be removed. 
As a general rule, the electrode should be large 
enough in diameter to equal the smallest diameter 



of a tap (the distance between the bottom of 
opposite flutes). To remove a stud, the electrode 
must not be so large that it could burn or damage 
the part if a slight misalignment is present. Use 
a scribe and a small magnet to remove any of the 
stud material not disintegrated. 



The coolant is pumped from a sump to the 
disintegrating head and then through the 
electrode, which is hollow, to the exact point of 
the disintegrating action. 

The specific controls which must be set may 
vary among the different machines; however, 
most have a control to start the disintegrating head 
vibrating and a selector switch for the heat or 



used. Some models have an automatic feed 
control that regulates the speed that the electrode 
penetrates the part to be removed. Regardless of 
whether the feed is automatic or manual, it must 
NOT be advanced so fast that it stops the 
disintegrating head and the electrode from 
vibrating. If this happens, the disintegrating 
action will stop and the electrode could be bent 
or broken. 



5-31 



OFFHAND GRINDING OF TOOLS 



One requirement for advancement in the MR 
rating is to demonstrate the ability to grind and 
sharpen some of the tools used in the machine 
shop. Equipment used for this purpose includes 
bench, pedestal, carbide, and chip breaker 
grinders and precision grinding machines. This 
chapter contains information on the use of these 
grinders and how to grind small tools by using 
the offhand grinding technique. (Precision 
grinding machines will be discussed in a later 
chapter.) 

Grinding is the removal of metal by the 
cutting action of an abrasive. In offhand grinding 
you hold the workpiece in your hand and position 
it as needed while grinding. To grind accurately 
and safely, using the offhand method, you must 
have experience and practice. In addition, you 
must know how to install grinding wheels on 
pedestal and bench grinders and how to sharpen 
or dress them. You must also know the safety 
precautions concerning grinding. 

To properly grind small handtools, single- 
edged cutting tools, and twist drills, you must 
know the terms used to describe the angles and 
surfaces of the tools. You must also know the 
composition of the material from which each tool 
is made and the operations for which the to6l is 
used. 



GRINDING SAFETY 

The grinding wheel is a fragile cutting tool 
which operates at high speeds. Therefore, the safe 
operation of bench and pedestal grinders is as 
important to you as are proper grinding 
techniques. Observance of safety precautions, 
posted on or near all grinders used by the Navy, 
is mandatory for your safety and the safety of 
personnel nearby. 

What are some the injuries that result from 
grinding operations? Eye injuries caused by grit 
generated during the grinding process are the most 
common and the most serious. Abrasions caused 



by bodily contact with the wheel are quite painful 
and can be serious. Cuts and bruises caused by 
segments of an exploding wheel, or a tool 
"kicked" away from the wheel are other sources 
of injury. Additionally, prior cuts and abrasions 
can become infected if they are not protected from 
grit and dust produced during grinding. 

Safety in using bench and pedestal grinders is 
primarily a matter of using common sense and 
concentrating on the job at hand. Each time you 
start to grind a tool, stop briefly to consider how 
the observance of safety precautions and the use 
of safeguards protect you from injury. Consider 
the complications that could be caused by loss of 
your sight, or loss or mutilation of an arm or 
hand. 

Some guidelines for safe grinding practices 



are: 



Secure all loose clothing and remove rings 
or other jewelry. 

Inspect the grinding wheel, wheel guards, 
toolrest, and other safety devices to ensure 
that they are in good condition and 
positioned properly. Set the toolrest so that 
it is within 1/8 inch of the wheel face and 
level with the center of the wheel. 

Clean and adjust transparent shields 
properly, if they are installed. Transparent 
shields do not protect against dust and grit 
that may get around a shield. You must 
ALWAYS wear goggles while grinding. 
Goggles with side shield give the best eye 
protection. 

Stand aside when starting the grinder 
motor until it has run for 1 minute. This 
prevents injury in case the wheel explodes 
from a defect that you did not notice. 

Use light pressure when you begin 
grinding; too much pressure on a cold 
wheel may cause the wheel to fail. 



6-1 



On bench and pedestal grinders, grind only 
on the face or periphery of a grinding 
wheel unless the grinding wheel is 
specifically designed for side grinding. 

Use a coolant to prevent the work from 
overheating. 



BENCH AND 
PEDESTAL GRINDERS 

Bench grinders (fig. 6-1) are small, self- 
contained grinders which are usually mounted on 
a workbench. They are used for grinding and 
sharpening small tools such as lathe, planer, and 
shaper cutting tools; twist drills; and handtools 
such as chisels and center punches. These grinders 
do not have installed coolant systems; however, 
a container of water is usually mounted on the 
front of the grinder. 

Grinding wheels up to 8 inches in diameter and 
1 inch in thickness are normally used on bench 
grinders. A wheel guard encircles the grinding 
wheel except for the work area. An adjustable 
toolrest steadies the workpiece and can be moved 
in or out or swiveled to adjust to grinding wheels 
of different diameters. An adjustable eye shield 
made of safety glass should be installed on the 
upper part of the wheel guard. Position this shield 
to deflect the grinding wheel particles away from 
you. 

Pedestal grinders are usually heavy duty bench 
grinders which are mounted on a pedestal fastened 
to the deck. In addition to the features of the 
bench grinder, pedestal grinders normally have 
a coolant system which includes a pump, storage 
sump, and a hose and fittings to regulate and carry 




the coolant to the wheel surface. Pedestal grinders 
are particularly useful for rough grinding such as 
"snagging" castings. Figure 6-2 shows a pedestal 
grinder in use. 

GRINDING WHEELS 

A grinding wheel is composed of two basic 
elements: (1) the abrasive grains, and (2) the 
bonding agent. The abrasive grains may be 
compared to many single point tools embedded 
in a toolholder or bonding agent. Each of these 
grains removes a very small chip from the 
workpiece as it makes contact on each revolution 
of the grinding wheel. 

An ideal cutting tool is one that will sharpen 
itself when it becomes dull. This, in effect, is what 
happens to the abrasive grains. As the individual 
grains become dull, the pressure that is generated 
on them causes them to fracture and present new 
sharp cutting edges to the work. When the grains 
can fracture no more, the pressure becomes too 
great and they are released from the bond, allow- 
ing new sharp grains to contact the work. 

SIZES AND SHAPES 

Grinding wheels come in various sizes and 
shapes. The size of a grinding wheel is determined 




Figure 6-1. Bench grinder. 



28.61 



Figure 6-2. Grinding on a pedestal grinder. 



spindle hole, and the width of its face. All the 
shapes of grinding wheels are too numerous to 
list in this manual, but figure 6-3 shows most of 
the frequently used wheel shapes. The type 



TYPEl 



STRAIGHT 



TYPE 2 



CYLINDER 



TYPE i 



CUT-OFF 





TYPE 6 STRAIGHT CUP 



TYPE 5 RECESSED ONE SIDE 




TYPE 7 RECESSED TWO SIDE 




TYPE 12 



DISH 



TYPE il 



TYPE 13 



FLARING CUP 



SAUCER 



Figure 6-3. Grinding wheel shapes. 



manufacturers. The shapes are shown in cross- 
sectional views. The specific job will dictate the 
shape of the wheel to be used. 

WHEEL MARKINGS AND 
COMPOSITION 

Grinding wheel markings are composed of six 
stations. Figure 6-4 illustrates the standard 
marking. The following information breaks down 
the marking and explains each station type of 
abrasive, grain size, bond grade, structure, type 
of bond, and the manufacturer's record symbol. 
Study this information carefully, as it will be 
invaluable to you in making the proper wheel 
selection for each grinding job you attempt. 

Type of Abrasive 

The first station of the wheel marking is the 
abrasive type. There are two types of abrasives: 
natural and manufactured. Natural abrasives, 
such as emery, corundum, and diamond, are used 
only in honing stones and in special types of 
grinding wheels. The common manufactured 
abrasives are aluminum oxide and silicon carbide. 
They have superior qualities and are more 
economical than natural abrasives. Aluminum 
oxide (designated by the letter A) is used for 



C 60 I 8 













ABRASIVE 


GRAIN 




TYPE 






SIZE 




A- ALUMINUM 






10 




OXIDE 






12 


-> 


C-SILICON 






14 




CARBIDE 






16 










18 










20 






24 




"- 


60 




1 




600 



\ 













BOND 
GRADE 


STRUCTURE 




A-SOFT 






1 - DENSE 




8 








2 






C 








3 






D 








4 






E 








5 






F 








6 






G 








7 






H-TO 




h 


J3 TO 


"fc 


I 




P 


9 






"j 






10 






K 






11 






L 






12 






M 






13 






N 






14 \ 






) 


t 




15- OPEN 




Z-HARD 










BOND 

TYPE 



V-VITRIFIED 
S SILICATE 
R-RU88ER 
B-RESINOID 
E-SHELLAC 

0-OXYCHLOR- 
IDE 




Figure 6-4. Standard marking system for grinding wheels (except diamond). 



6-3 



work such as cleaning up steel castings. Silicon 
carbide (designated by the letter C), which is 
harder but not as tough as aluminum oxide, is 
used mostly for grinding nonferrous metals and 
carbide tools. The abrasive in a grinding wheel 
comprises about 40% of the wheel. 



Grain Size 

The second station of the grinding wheel 
marking is the grain size. Grain sizes range from 
10 to 500. The size is determined by the size of 
mesh of a sieve through which the grains can pass. 
Grain size is rated as follows: Coarse: 10, 12, 14, 
16, 18, 20, 24; Medium: 30, 36, 46, 54, 60; Fine: 
70, 80, 90, 100, 120, 150, 180; and Very Fine: 220, 
240, 280, 320, 400, 500, 600. Grain sizes finer than 
240 are generally considered to be flour. Fine grain 
wheels are preferred for grinding hard materials, 
as they have more cutting edges and will cut faster 
than coarse grain wheels. Coarse grain wheels are 
generally preferred for rapid metal removal on 
softer materials. 



Bond Grade (Hardness) 

Station three of the wheel marking is the grade 
or hardness of the wheel. As shown in figure 6-4, 
the grade is designated by a letter of the alphabet; 
grades run from A to Z, or soft to hard. 

The grade of a grinding wheel is a measure 
of the bond's ability to retain the abrasive grains 
in the wheel. The grading of a grinding wheel from 
soft to hard grade does not mean that the bond 
or the abrasive is soft or hard; it means that the 
wheel has either a small amount of bond (soft 
grade) or a large amount of bond (hard grade). 
Figure 6-5 shows magnified portions of both soft 
grade and hard grade wheels. You can see by the 
illustration that a part of the bond surrounds the 
abrasive grains, and the remainder of the bond 
forms into posts which both hold the grains to 
the wheel and hold them apart from each other. 
The wheel with the larger amount of> bonding 
material has thick bond posts and will offer great 
resistance to pressures generated in grinding. The 
wheel with the least amount of bond will offer 
less resistance to the grinding pressures. In other 
words, the wheel with a large amount of bond is 
a hard grade and the wheel with a small amount 
of bond is a soft grade. 




ABKASIVE 
GRAIN 

BOND 
" COATING 

OPEN SPACE 
BOND POST 



m 



WHEEL A 




WHEEL B 



Figure 6-5. How bond affects the grade of the wheel. Wheel 
A, softer; wheel B, harder. 



Structure 

The fourth station of the grinding wheel 
marking is the structure. The structure is 
designated by numbers from 1 to 15, as illustrated 
in figure 6-4. The structure of a grinding wheel 
refers to the open space between the grains, as 
shown in figure 6-5. Wheels with grains that are 
very closely spaced are said to be dense; when 
grains are wider apart, the wheels are said to be 
open. The metal removal will be greater for open- 
grain wheels than for close-grain wheels. Also 
dense, or close grain, wheels will normally pro- 
duce a finer finish. The structure of a grinding 
wheel comprises about 20% of the grinding wheel. 

Bond Type 

The fifth station of the grinding wheel mark- 
ing is the bond type. The bond comprises the 
remaining 40% of the grinding wheel and is one 
of the most important parts of the wheel. The 
bond determines the strength of the wheel. The 



6-4 



VITRIFIED BOND. Designated by the 
letter V, this is the most common bond used in 
grinding wheels. Approximately 15% of all 
grinding wheels are made with vitrified bond. This 
bond is not affected by oil, acid, or water. 
Vitrified bond wheels are strong and porous, and 
rapid temperature changes have little or no effect 
on them. Vitrified bond is composed of special 
clays. When heated to approximately 2300 F the 
clays form a glass-like cement. Vitrified wheels 
should not be run faster than 6500 surface feet 
per minute. 

SILICATE BOND. Silicate bond wheels are 
designated by the letter S. The bond is made of 
silicate of soda. Silicate bond wheels are used 
mainly for large, slow rpm machines where a 
cooler cutting action is desired. Silicate bond 
wheels are softer than vitrified wheels; they release 
the grains more readily than vitrified wheels. 
Silicate bond wheels are heated to approximately 
500 F when they are made. This type of wheel, 
like the vitrified bond wheel, must not be run at 
a speed greater than 6500 surface feet per minute. 

RUBBER BOND. Rubber bond wheels are 
designated by the letter R. The bond consists of 
rubber with sulphur added as a vulcanizing agent. 
The bond is made into a sheet into which the 
grains are rolled. The wheel is stamped out of this 
sheet and heated in a pressurized mold until the 
vulcanizing action is completed. Rubber bond 
wheels are very strong and are elastic. They are 
used for thin cutoff wheels. Rubber bond wheels 
produce a high finish and can be run at speeds 
between 9,500 and 16,000 surface feet per minute. 

RESINOID BOND. Resinoid bond wheels 
are designated by the letter B. Resinoid bond is 
made from powdered or liquid resin with a 
plasticizer added. The wheels are pressed and 
molded to size and fired at approximately 320 F. 
Resinoid wheels are shock resistant and very 
strong. They are used for rough grinding and as 
cutoff wheels. Resinoid wheels, like rubber bond 
wheels, can be run at a speed of 9,500 to 16,000 
surface feet per minute. 

SHELLAC BOND. Shellac bond wheels are 
designated by the letter E. Wheels of this type are 
made from a secretion from Lac bugs. The 
abrasive and bond are mixed and molded to shape 



cutting action when used as cutoff wheels. Shellac 
bond wheels can be run at speeds between 9,500 
and 12,500 surface feet per minute. 

OXYCHLORIDE BOND. Oxychloride 
bond wheels are designated by the letter O. 
Oxychloride bond is made from chemicals and is 
a form of cold-setting cement. This bond is 
seldom used in grinding wheels but is used 
extensively to hold abrasives on sanding disks. 
Oxychloride bond wheels can be run at speeds 
between 5,000 and 6,500 surface feet per minute. 



Manufacturer's Record Symbol 

The sixth station of the grinding wheel 
marking is the manufacturer's record. This may 
be a letter or number, or both. It is used by the 
manufacturer to designate bond modifications or 
wheel characteristics. 



DIAMOND WHEELS 

Diamond grinding wheels are classed by 
themselves. Wheels of this type are very 
expensive and should be used with care and only 
for grinding carbide cutting tools. Diamond 
wheels can be made from natural or manufactured 
diamonds. They are marked similarly to 
aluminum-oxide and silicon-carbide wheels, 
although there is not a standard system. The first 
station is the type of abrasive, designated D for 
natural and SD for manufactured. The second 
station is the grit size, which can range from 24 
to 500. A 100-grain size might be used for rough 
work, and a 220 for finish work. In a Navy 
machine shop, you might find a 150-grain wheel 
and use it for both rough and finish grinding. The 
third station is the grade, designated by letters of 
the alphabet. The fourth station is concentration, 
designated by numbers. The concentration or 
proportion of diamonds to bond might be 
numbered 25, 50, 75, or 100, going from low to 
high. The fifth station is the bond type, designated 
B for resinoid, M for metal, and V for vitrified. 
The sixth station may or may not be used; when 
used it identifies bond modification. The seventh 
station is the depth of the diamond section. This 
is the thickness of the abrasive layer and ranges 
from 1/32 to 1/4 inch. Cutting speeds range from 
4,500 to 6,000 surface feet per minute. 



6-5 



GRAIN DEPTH OF CUT 

On most ships, stowage space is limited. 
Consequently, the inventory of grinding wheels 
must be kept to a minimum. It would be 
impractical and unnecessary to keep on hand a 
wheel for every grinding job. With a knowledge 
of the theory of grain depth of cut you can vary 
the cutting action of the various wheels and with 
a small inventory can perform practically any 
grinding operation that may be necessary. 

For ease in understanding this theory, assume 
that a grinding wheel has a single grain. When 
the grain reaches the point of contact with the 



work, the depth of cut is zero. As the wheel and 
the work revolve, the grain begins cutting into the 
work, increasing its depth of cut until it reaches 
a maximum depth at some point along the arc of 
contact. This greatest depth is called the grain 
depth of cut. 

To understand what part grain depth of cut 
plays in grinding, look at figure 6-6. Part A 
illustrates a grinding wheel and a workpiece; 
ab is the radial depth of cut, ad is the arc of 
contact, and ef is the grain depth of cut. As the 
wheel rotates, the grain moves from the point of 
contact a to d in a given amount of time. During 
the same time, a point on the workpiece rotates 



RADIAL 

DEPTH 

OF CUT ob 




ORIGINAL 
WHEEL 



amount of material represented by the shaded area 
ade. Now refer to part B and assume that the 
wheel has worn down to a much smaller size, 
while the wheel and work speeds remain un- 
changed. The arc of contact ad' of the smaller 
wheel is shorter than the arc of contact ad of the 
original (larger) wheel. Since the width of the 
grains remains the same, decreasing the length of 
the arc of contact will decrease the surface 
(area = length x width) that a grain on the smaller 
wheel covers in the same time as a grain on the 
larger wheel. If the depth that each grain cuts into 
the workpiece remains the same, the grain on the 
smaller wheel will remove a smaller volume 
(volume = length x width x depth) of material in 
the same time as the grain on the larger wheel. 
However, for both grains to provide the same 
cutting action, they both have to remove the same 
volume of material in the same length of time. 
To make the volume of material the grain on the 
smaller wheel removes equal that of the grain on 
the larger wheel, you have to either make the grain 
on the smaller wheel cut deeper into the workpiece 
or cover a larger workpiece surface area at its 
original depth of cut. 

To make the grain cut deeper, you must 
increase the feed pressure on the grain. This 
increase of feed pressure will cause the grain to 
be torn from the wheel sooner, making the wheel 
act like a softer wheel. Thus, the grain depth of 
cut theory says that as a grinding wheel gets 
smaller, it will cut like a softer wheel because of 
the increase in feed pressure required to maintain 
its cutting action. 

The opposite is true if the wheel diameter 
increases. For example, if you replace a wheel that 
is too small with a larger wheel, you must decrease 
feed pressure to maintain the same cutting action. 

The other previously mentioned way to make 
a grain on a smaller wheel remove the same 
amount of material as a grain on a larger wheel 
is to keep the depth of cut the same (no increase 
in feed pressure) while you increase the surface 
area the grain contacts. Increasing the surface area 
requires lengthening the contact area, since the 
width remains the same. To lengthen the contact 
area, you can either speed up the workpiece 
rotation or slow down the wheel rotation. Either 
of these actions will cause a longer surface strip 
of the workpiece to come in contact with the grain 
on the wheel, thereby increasing the volume of 
material removed. 



removing a larger volume of material, you must 
decrease the surface of the workpiece with which 
the grain comes into contact. You can do this by 
either slowing down the workpiece rotation or 
speeding up the wheel rotation. 

Keep in mind that all of these actions are based 
on the grain depth of cut theory. That is, making 
adjustments to the grinding procedure to make 
one wheel cut like another. The following 
summary shows the actions you can take to make 
a wheel act a certain way. 

MAKE THE WHEEL ACT SOFTER (IN- 
CREASE THE GRAIN DEPTH OF CUT) 

Increase the work speed 
Decrease the wheel speed 

Reduce the diameter of the wheel and 
increase feed pressure 

MAKE THE WHEEL ACT HARDER 
(DECREASE THE GRAIN DEPTH OF 
CUT) 

Decrease the work speed 
Increase the wheel speed 

Increase the diameter of the wheel and 
decrease feed pressure 

GRINDING WHEEL SELECTION 
AND USE 

The selection of grinding wheels for precision 
grinding is based on such factors as the physical 
properties of the material to be ground, the 
amount of stock to be removed (depth of cut), 
the wheel speed and work speed, and the finish 
required. The selection of a grinding wheel that 
has the proper abrasive, grain, grade, and bond 
is determined by one or more of these factors. 

An aluminum oxide abrasive is the most 
suitable for grinding carbon and alloy steel, high- 
speed steel, cast alloys and malleable iron. A 
silicon carbide abrasive is the most suitable for 
grinding nonferrous metals, nonmetallic 
materials, and cemented carbides. 

Generally, as you grind softer and more 
ductile materials, you should select coarser grain 
wheels. Also, if you need to remove a large 
amount of material, use a coarse grain wheel 
(except on very hard materials). If a good finish 
is required, use a fine grain wheel. If the machine 



6-7 



you are using is worn, use may need to use a 
harder grade to help offset the effects of wear on 
the machine. Using a coolant also permits you to 
use a harder grade of wheel. Table 6-1 lists 
recommended grinding wheels for various 
operations. 

Figure 6-7 shows the type of grinding wheel 
used on bench and pedestal grinders. When you 
replace the wheel be sure that the physical 
dimensions of the new wheel are correct for the 
grinder on which it will be used. The outside 
diameter, the thickness, and the spindle hole size 
are the three dimensions that you must check. If 
necessary, use an adapter (bushing) to decrease 
the size of the spindle hole, so that it fits your 
grinder. 

The wheels recommended for grinding and 
sharpening single point (lathe, planer, shaper, and 
so on) tool bits made from high-carbon steel or 




STRAIGHT WHEEL 
Figure 6-7. Grinding wheel for bench and pedestal grinders. 



high-speed steel are A3605V (coarse wheel) and 
A60M5V (fine or finish wheel). Stellite tools 
should be ground on a wheel designated A46N5V. 
These grinding wheels, which have aluminum 
oxide as an abrasive material, should be used to 
grind steel and steel alloys only. Grinding cast 
iron, nonferrous metal or nonmetallic materials 
with these grinding wheels will result in loading 
or pinning of the wheel as the particles of the 
material being ground become imbedded in the 



Table 6-1. Recommendations for Selecting Grinding Wheels 



OPERATION 


WHEEL DESIGNATION 


MATERIAL 


Abrasive 


Grain 
size 


Grade 


Structure 


Bond 


Mfg. 
Symbol 


Cylindrical 
grinding 


A 
A 
A 
A 
C 

A 
A 


60 
60 
54 
36 
36 

60 
54 


K 
L 
M 
G 
K 

G 
L 


8 

5 
5 
12 
5 

12 
5 


V 
V 
V 
V 
V 

V 
V 




High-speed steel 
Hardened steel 
Soft steel 
Stainless steel 
Cast iron, brass, 
aluminum 
Nickel copper 
(Monel) 
General purpose 
















Surface grinding 


A 

A 
A 

A 
C 

A 
A 


46 
60 
46 
36 
36 

60 

24 


H 
F 
J 
G 
J 

G 
H 


8 
12 
5 
12 
8 

12 
8 


V 
V 

V 
V 
V 

V 
V 




High-speed steel 
Hardened steel 
Soft steel 
Stainless steel 
Cast iron and 
bronze 
Nickel copper 
(Monel) 
General purpose 
















Tool and 
cutter grinding 


A 

A 
A 


46 

54 
60 


K 

L 
K 


8 

5 
8 


V 

V 
V 




High-speed steel or 
cast alloy milling 
cutter 
Reamers 
Taps 









and possibly injure someone nearby. 
WHEEL INSTALLATION 

The wheel of a bench or pedestal grinder must 
be properly installed; otherwise, the wheel will not 
operate properly and accidents may occur. Before 
a wheel is installed, it should be inspected for 
visible defects and "sounded" to determine 
whether it has invisible cracks. To properly sound 
a wheel, hold it up by placing a hammer handle 
or a short piece of cord through the spindle hole. 
Using a nonmetallic object such as a screwdriver 
handle or small wooden mallet, tap the wheel 
lightly on its side. Rotate the wheel 1/4 of a turn 
(90) and repeat the test. A good wheel gives out 
a clear ringing sound when tapped. If the tapping 
produces a dull thud, the wheel is cracked and 
should not be used. 

You will find it easier to understand the 
following information on mounting the wheel if 
you refer to figure 6-8. Ensure that the shaft and 
flanges are clean and free of grit and old blotter 
material. Place the inner flange in place and 




inch and no thicker than 0.125 inch for leather 
or rubber. The blotter is used to ensure even 
pressure on the wheel and to dampen the vibration 
between the wheel and the shaft when the grinder 
is operating. 

Next, mount the wheel, and ensure that it fits 
on the shaft without play, there should be a 0.002- 
to 0.005 -inch clearance. You may need to scrape 
or ream the lead bushing in the center of the wheel 
to obtain this clearance. NEVER FORCE THE 
WHEEL ONTO THE SHAFT. Forcing the wheel 
onto the shaft may cause the wheel either to be 
slightly out of axial alignment or to crack when 
it is used. 

The next item to install is another blotter, 
followed by the outer flange. NOTE: the flanges 
are recessed so they provide an even pressure on 
the wheel. The flanges should be at least one-third 
the diameter of the wheel. 

Next, install the washer and secure the nut. 
Tighten the securing nut sufficiently to hold the 
wheel firmly; tightening too much may damage 
the wheel. 

TRUING AND DRESSING 
THE WHEEL 

Grinding wheels, like other cutting tools, 
require frequent reconditioning of cutting surfaces 
to perform efficiently. Dressing is the process of 
cleaning their cutting face. This cleaning breaks 
away dull abrasive grains and smoothes the 
surface so that there are no grooves. Truing is the 
removal of material from the cutting face of the 
wheel so that the resulting surface runs absolutely 
true to some other surface such as the grinding 
wheel shaft. 

The wheel dresser shown in figure 6-9 is used 
for dressing grinding wheels on bench and 



SAFETY HOOD 
WHEEL- 




Figure 6-8. Method of mounting a grinding wheel. 



Figure 6-9. Using a grinding wheel dresser. 



6-9 



pedestal grinders. To dress a wheel with this tool, 
start the grinder and let it come up to speed. Set 
the wheel dresser on the rest as shown in figure 
6-9 and bring it in firm contact with the wheel. 
Move the wheel dresser across the periphery 
of the wheel until the surface is clean and 
approximately square with the sides of the wheel. 
If grinding wheels get out of balance because 
of out-of-roundness, dressing the wheel will 
usually remedy the condition. A grinding wheel 
can get out of balance if part of the wheel is 
immersed in coolant. If this happens, remove the 
wheel and dry it out by baking. If the wheel gets 
out of balance axially, it probably will not affect 
the efficiency of the wheel on bench and pedestal 
grinders. This unbalance may be remedied simply 
by removing the wheel and cleaning the shaft 
spindle and spindle hole in the wheel and the 
flanges. 



CARBIDE TOOL GRINDER 

The carbide tool grinder (fig. 6-10) looks much 
like a pedestal grinder with the toolrest on the side 
instead of on the front. The main components of 
the carbide tool grinder are: a motor with the shaft 
extended at each end for mounting the grinding 
wheels; the pedestal which supports the motor and 
is fastened to the deck; wheel guards which are 
mounted around the circumference and back of 




the grinding wheels as a safety device; and an 
adjustable toolrest mounted in front of each wheel 
for supporting the tool bits while they are being 
ground. 

Unlike the pedestal grinder where the grinding 
is done on the periphery of the wheel, the carbide 
tool bit grinder has the grinding done on the side 
of the wheel. The straight cup wheel (fig. 6-11) 
is similar to the wheels used on most carbide tool 
bit grinders. Some carbide tool grinders have a 
straight cup wheel on one side of the grinder and 
a straight wheel, such as the type used on a 
pedestal or bench grinder, on the other side. 

The adjustable toolrest has an accurately 
ground groove or keyway across the top of its 
table. This groove is for holding a protractor 
attachment which can be set to the desired cutting 
edge angle. The toolrest will also adjust to permit 
grinding the relief angle. 

Some carbide tool grinders have a coolant 
system. When coolant is available, the tool should 
have an ample, steady stream of coolant directed 
at the point of grinding wheel contact. An ir- 
regular flow of coolant may allow the tool to heat 
up and then be quenched quickly, resulting in 
cracks to the carbide. If no coolant system is 
available, do NOT dip the carbide into a container 
of water when it becomes hot. Allow it to air cool. 

Carbide tipped tool bits may have tips that are 
(1) disposable, having three or more pre-ground 
cutting edges or (2) brazed, having cutting edges 
that must be ground. The disposable-tip type tool 
bit needs no sharpening; the tips are disposed of 
as their cutting edges become dull. The brazed- 
tip type tool bit is sharpened on the carbide tool 
bit grinder. 

For best results in sharpening carbide tipped 
tool bits, use a silicon carbide wheel for roughing 
and a diamond impregnated wheel for finishing. 



WORKING FACE 




Figure 6-10. Carbide tool grinder. 



Figure 6-11. Crown on the working face of a wheel for a 
carbide tool bit grinder. 



You can obtain the best results from carbide 
tipped tools by using four different grinding 
wheels to sharpen them. Use the aluminum 
oxide wheel recommended for grinding high-speed 
steel tools to grind the steel shank beneath the 
carbide tip to the desired end and side cutting edge 
angles with a relief angle of approximately 15 . 
This angle is approximately double the clearance 
angle ground on the carbide tip. When you are 
ready to grind the carbide tip, use wheels that have 
silicon carbide as the abrasive material. Use a 
C6018V wheel for rough grinding and a C100H8V 
wheel for semifinish grinding. To finish grind the 
tip, use a diamond impregnated grinding wheel 
with the designation SD 220-P50V. 



OPERATION OF THE CARBIDE 
TOOL GRINDER 

Use the following procedure to sharpen a 
carbide tipped tool bit. 

Using a grinder with an ALUMINUM 
OXIDE wheel, grind side relief and end 
relief angles on the STEEL shanks. 
Caution: NEVER grind steel shanks with 
silicon carbide wheels. 

Dress the silicon carbide wheel with a star 
type wheel dresser. Form a 1/16-inch 
crown on the working face of the wheel 
to minimize the amount of contact be- 
tween the tip and the wheel (fig. 6-11). 

Using the graduated dial on the side of the 
toolrest, adjust the toolrest to the desired 
side clearance angle. 

Place the protractor on the toolrest with 
the protractor key in the key way. Set the 
protractor to the proper side cutting edge 
angle. 

Hold the shank of the tool bit firmly 
against the side of the protractor; move the 
tool bit back and forth across the wheel, 
keeping a steady, even pressure against the 
wheel. To prevent burning the carbide tip, 
keep the tool bit continually in motion 
while grinding it. 



Generally, when a carbide tool chip grinder 
is available, the finish grinding operation is 
performed on this machine with a diamond wheel. 
The chip grinder is very similar to the carbide tool 
bit grinder except that the wheels are smaller and 
diamond impregnated. 

If you use silicon carbide wheels, grind the car- 
bide tip dry. If you use diamond wheels, be sure 
to use coolant on both the tool and the wheel face. 
NEVER allow the steel shank to come into con- 
tact with a diamond wheel as this will immediately 
load the wheel. 



CHIP BREAKER GRINDER 

A chip breaker grinder (fig. 6-12) is a 
specialized grinding machine. It is designed 
to permit accurate grinding of grooves or 




Figure 6-12. Chip breaker grinder. 



6-11 



indentations on the top surface of carbide tools, 
so that the direction and length of the chips 
produced in cutting metal can be controlled. A 
description of the various types of chip breakers 
that are commonly ground on carbide tools will 
be presented later in this chapter. 

The chip breaker grinder has a vise which can 
be adjusted to four different angles to hold the 
tool to be ground. These angles the side cutting 
edge, back rake, side rake, and the chip 
breaker are explained later in this chapter. The 
vise is mounted so it can be moved back and forth 
under the grinding wheel. Both the cross feed, for 
positioning the tool under the grinding wheel, and 
the vertical feed, for controlling the depth of the 
chip breaker, are graduated in increments of 0.001 
inch. 

A diamond wheel is used on the chip breaker 
grinder. The wheel is usually a type 1 straight 
wheel but differs from other type 1 wheels in that 
it is normally less than 1/4 inch thick. An 
SD150R100B grinding wheel is normally 
recommended. 

Chip breaker grinders have a coolant system 
that either floods or slowly drips coolant onto the 
tool being ground. The main objective in using 



coolant is to prevent the grinding wheel from 
loading up or glazing over from the grinding 
operation. 

SINGLE-POINT CUTTING TOOLS 

A single-point or single-edged cutting tool is 
a tool which has only one cutting edge as opposed 
to two or more cutting edges. Drill bits are 
multiple-edged cutters; most lathe tools are single 
edged. To properly grind a single-point cutting 
tool, you must know the relief angles, the rake 
angles, and the cutting edge angles that are 
required for specific machines and materials. You 
must know also what materials are generally used 
for cutting tools and how tools for various 
machines differ. 

Cutting Tool Terminology 

Figure 6-13 shows the application of the angles 
and surfaces we use in discussing single-point 
cutting tools. Notice that there are two relief 
angles and two rake angles and that the angle of 
keenness is formed by cutting a rake angle and 
a relief angle. 



SIDE RAKE ANGLE 



A 



FRONT 
VIEW 




B 



BACK RAKE ANGLE 
\ 




RIGHT 
SIDE 
VIEW 



END RELIEF ANGLE 



NOSE 




SIDE CUTTING EDGE ANGLE 



making a slope either away from or toward the 
side cutting edge. Figure 6-1 3A shows a positive 
side rake angle. When the side rake is cut toward 
the side cutting edge, the side rake has a negative 
angle. The amount of side rake influences to some 
extent the size of the angle of keenness. It causes 
the chip to "flow" to the side of the tool away 
from the side cutting edge. A positive side rake 
is most often used on ground single-point tools. 
Generally, the side rake angle will be steeper (in 
the positive direction) for cutting the softer metals 
and will decrease as the hardness of the metal 
increases. A steep side rake angle in the positive 
direction causes the chip produced in cutting to 
be long and stringy. Decreasing the angle will 
cause the chip to curl up and break more quickly. 
A negative side rake is recommended when the 
tool will be subjected to shock, such as an 
interrupted cut or when the metal being cut is 
extremely hard. 

BACK RAKE. The back rake is the angle at 
which the top surface of the tool is ground away 
mainly to guide the direction of the flowing chips. 
It is ground primarily to cause the chip cut by the 
tool to "flow" back toward the shank of the tool. 
Back rake may be positive or negative; it is 
positive (fig. 6-13B) if it slopes downward from 
the nose of the tool toward the shank, or negative 
if a reverse angle is ground. The rake angles aid 
in forming the angle of keenness and in directing 
the chip flow away from the point of cutting. 
The same general recommendations concerning 
positive or negative side rake angles apply to the 
back rake angle. 

SIDE RELIEF. The side relief (fig. 6-13A) 
is the angle at which the side of the tool is ground 
to prevent the tool bit from rubbing into the work. 
The side relief angle, like the side rake angle, 
influences the angle of keenness. A tool with 
proper side relief causes the side thrust to be 
concentrated on the cutting edge rather than 
rubbing on the flank of the tool. 

END RELIEF. The end relief (fig. 6-13B) 
is the angle at which the end surface of the tool 
is ground so that the front face edge of the tool 
leads the front surface. 

ANGLE OF KEENNESS. The angle of 
keenness or wedge angle (fig. 6- 13 A) is formed 



the sum of the side rake and side relief angles. 
Generally, for cutting soft materials this angle is 
smaller than for cutting hard materials. 

SIDE CUTTING EDGE. The side cutting 
edge angle (fig. 6-13C) is ground on the side of 
the tool that is fed into the work. This angle can 
vary from for cutting to a shoulder, up to 30 
for straight turning. An angle of 15 is 
recommended for most rough turning operations. 
In turning long slender shafts, a side cutting edge 
angle that is too large can cause chatter. Since the 
pressure on the cutting edge and the heat 
generated by the cutting action decrease as the side 
cutting edge angle increases, the angle should be 
as large as the machining operation will allow. 

END CUTTING EDGE. The end cutting 
edge angle (fig. 6-13C) is ground on the end of 
the tool to permit the nose to make contact with 
the work without the tool dragging the surface. 
An angle of from 8 to 30 is commonly used with 
approximately 15 recommended for rough 
urning operations. Finish operations can be made 
with the end cutting edge angle slightly larger. Too 
large an end cutting edge angle will reduce the 
support given the nose of the tool and could cause 
premature failure of the cutting edge. 

NOSE. The nose (fig. 6-13C) strengthens the 
tip of the tool, helps to carry away the heat 
generated by the cutting action and helps to obtain 
good finish. A tool that is used with the nose 
ground to a straight point will fail much more 
rapidly than one which has had a slight radius 
ground or honed on it. However, too large a 
radius will cause chatter because of excessive tool 
contact with the work. A radius (rounded end) 
of from 1/64 to 1/32 inch is normally used for 
turning operations. 



GROUND-IN CHIP BREAKERS 

Chip breakers are indentations ground on the 
top surface of the tool that help reduce or prevent 
the formation of long and dangerous chips. The 
chip breaker will cause the chips to curl up and 
break into short, safe, manageable chips. Chip 
breakers are ground mostly on roughing tools, but 
they can be ground on finishing tools used to 



6-13 



machine soft ductile metals. Figure 6-14 shows 
four of the several types of chip breakers that can 
be ground onto the cutting tool. 

The dimensions given are general and can be 
modified to compensate for the various feed rates, 
depths of cut, and types of material being 
machined. The groove type chip breaker must be 
carefully ground to prevent it from coming too 
close to the cutting edge which reduces the life 
of the tool due to decreased support of the cutting 
edge. Chip breakers on carbide tipped tools can 
be ground with the diamond wheel on the chip 
breaker grinder. High-speed tools must be ground 
with an aluminum oxide grinding wheel. This can 
be done on a bench grinder by dressing the wheel 
until it has a sharp edge or by using a universal 
vise which can be set to compound angles on a 
mrface or tool and cutter grinder. 



CUTTING TOOL MATERIALS 

The materials used to make machine cutting 
tools must have the hardness necessary to cut 
other metals, be wear resistant, have impact 
strength to resist fracture, and be able to 
retain their hardness and cutting edge at high 
temperatures. Several different materials are 
used for cutting tools and each one has 
properties different from the others. Selection of 
a specific cutting tool material depends on the 
metal being cut and conditions under which the 
cutting is being done. 







TOP VIEWS 

'/6- 3 /l6 1/32 

ijjll/'' , lit I/" 




'/32 



PARALLEL SHOULDER GROOVE ANGULAR 

END VIEWS. 
Figure 6-14. Chip breakers. 



CARBON TOOL STEEL 

The carbon steel used to make cutting tools 
usually contains from 0.90% to 1.40% carbon. 
Some types contain small amounts of chrome or 
vanadium to increase the degree of hardness or 
toughness. Carbon steel is limited in its use as a 
cutting tool material because of its low tolerance 
to the high temperatures generated during the 
cutting process. Tools made from carbon steel will 
begin to lose their hardness, 50 to 64 Rockwell 
"C," at a tempering range of approximately 350 
to 650 F. Carbon steel tools perform best as lathe 
cutting tools when used to take light or finishing 
cuts on relatively soft materials such as brass, 
aluminum, and unhardened low carbon steels. 
The cutting speed for carbon steel tools 
should be approximately 50% of the speeds 
recommended for high-speed steel tools. 

HIGH-SPEED STEEL 

High-speed steel is probably the most common 
cutting tool material used in Navy machine shops. 
Unlike carbon steel tools, high-speed steel tools 
are capable of maintaining their hardness and 
abrasion resistance under the high temperatures 
and pressures generated during the general cutting 
process. Although the hardness of the high-speed 
tool (60 to 70 Rockwell ''C") is not much greater 
than that of carbon steel tools, the tempering 
temperature at which high-speed steel begins to 
lose its hardness is 1000 to 1100F. There are 
two types of high-speed tools which are generally 
used in machine shops. They are tungsten high- 
speed steel and molybdenum high-speed steel. 
These designations are used to indicate the major 
alloying element in each of the two types. Both 
types are similar in their ability to resist abrasive 
wear and to remain hard at high temperatures, 
and in their degree of hardness. The molybdenum 
type high-speed steel is tougher than the tungsten 
type and is more effective in machinery operations 
where interrupted cuts are made. 

During interrupted cuts, such as cutting out- 
of-round or slotted material, the cutter contacts 
the material many times in a short period of time. 
This "hammering" effect dulls or breaks cutters 
which are not tough enough to withstand the 
shock effect. 

CAST ALLOYS 

Cast alloy tool steel usually contains varying 
amounts of cobalt, chrome, tungsten, and 



C. \ A 



high-speed steel, retaining their hardness up to 
an operating temperature of approximately 
1400F. This characteristic allows cutting speeds 
approximately 60% greater than for high-speed 
steel tools. However, cast alloy tools are not as 
tough as the high-speed steel tools and therefore 
cannot be subjected to the same cutting stresses, 
such as interrupted cuts. Clearances that are 
ground on cast alloy cutting tools are less than 
those ground on high-speed steel tools because of 
the lower degree of toughness. Tools made from 
this metal are generally known as Stellite, 
Rexalloy, and Tantung. 

CEMENTED CARBIDE 

Cemented carbides, or sintered carbides as 
they are sometimes called, can be used at cutting 
speeds of two to four times those listed for high- 
speed steel. The softest carbide grade is equal in 
hardness to the hardest tool steel and is capable 
of maintaining its hardness and abrasive resistance 
up to approximately 1700F. Carbide is much 
more brittle than any of the other cutting tool 
materials previously described in this chapter. 
Because of this, interrupted cuts should be 
avoided and the machine setup should be as rigid 
and vibration free as possible. There are many 
different grades of carbides, each grade being 
more suited for a particular machining operation 
and metal than the others. Carbide manufacturers 
normally have available charts that match the 
correct grade for any given cutting application. 
Due to the brittleness of carbide, it is seldom used 
in a solid form as a cutting tool. The most 
common usage is as a tip on a steel shank or on 
the cutting edge of a twist drill. Carbide tipped 
lathe cutting tools are usually in the form of 
carbide tips brazed onto the end of a steel shank 
or as small variously shaped inserts, mechanically 
held on the end of a steel shank. A brief 
description of these two types of cutters is 
included in the following paragraphs. 

Brazed on Tip 

The brazed on carbide tip cutting tool was the 
first carbide cutting tool developed and made 
available to the metal cutting industry. The 
insert type of carbide tip has become more widely 
used because of the ease in changing cutting 
edges. There are some jobs which have shapes that 
cannot be readily machined with a standard 



of tools required in machinery, such as turning, 
facing, threading, and grooving are available with 
different grades of carbide tips already brazed 
onto steel shanks. Small carbide blanks are also 
available that you can braze onto a shank. 

Brazing on a carbide tip is a relatively simple 
operation that can be performed by anyone 
qualified to operate an oxy acetylene torch. To 
braze on a carbide tip, first, thoroughly clean the 
steel shank by grinding or sandblasting and 
degreasing it with an approved solvent. Next, 
completely coat the steel shank and the carbide 
tip with a flux to further remove any contamina- 
tion and to prevent oxidation during brazing. A 
thin shim-like brazing alloy is available that you 
can cut to the size needed and place between the 
shank and the carbide tip. This type of bronze 
alloy is better than the rod type because it results 
in a more uniform and stronger bronze. Begin 
heating the tool at the bottom of the shank. Raise 
the temperature slowly until the bronze alloy 
melts. Tap the carbide tip gently to ensure a firm 
seat onto the shank and then let the tool cool in 
the air. Quenching the tool in water will either 
cause the carbide tip to crack or prevent the 
bronze bond from holding the tip in place. After 
the tool is cooled, grind it to the shape desired. 

Chip control, when cutting tools with 
brazed-on carbide tips are used, may be provided 
by either feeds and speeds or by chip breaker 
grooves ground into the top of the carbide tip. 
Using a chip breaker grinder with a diamond 
impregnated wheel is the best way to grind a chip 
breaker. However, it is possible to use a carbide 
tool grinder or a pedestal grinder wheel dressed 
so that it has a sharp edge. The depth of the chip 
breakers averages about 1/32 inch, while the 
width varies with the feed rate, depth of cut and 
material being cut. Grind the chip breaker narrow 
at first and widen it if the chip does not curl and 
break quickly enough. You may also use these 
same types of chip breakers on high-speed steel 
cutters. 

Mechanically Held Tip (Insert Type) 

Mechanically held carbide inserts are available 
in several different shapes round, square, 
triangular, diamond threading, and grooving 
and in different thicknesses, sizes, and nose radii. 
The inserts may have either a positive, a neutral, 
or a negative rake attitude to the part being cut. 
The rake attitude is a combination of the back 
rake of the toolholder, the amount of clearance 



6-15 



ground along the edge of the insert beneath the 
cutting edge, and the ground-in chip breaker. 

An insert and its toolholder must have the 
same direction of rake. For instance, a negative 
rake toolholder requires a negative rake insert. 
Whenever possible, select the negative rake set-up 
because both sides of the insert can be used, thus 
doubling the number of cutting edges available 
on positive or neutral inserts. Be sure to place a 
specially made shim, having the same shape as the 
insert, into the toolholder pocket beneath the 
insert to provide a smooth and firm support for 
the insert. Methods of holding the insert in the 
toolholder vary from one manufacturer to 
another. Some inserts are held in place by the cam- 
lock action of a screw positioned through a hole 
in their centers, while others are held against the 
toolholder by a clamp. 

Chip control for carbide insert tooling is 
provided by two different methods. Some inserts 
have a groove ground into their cutting surfaces. 
Other inserts have a chip breaker plate held by 
a clamp on top of their cutting surfaces. 

CERAMIC 

Other than diamond tools, ceramic cutting 
tools are the hardest and most heat resistant 
cutting tools available to the machinist. A ceramic 
cutting tool is capable of machining metals that 
are too hard for carbide tools to cut. Additionally, 
ceramic can sustain cutting temperatures of up to 
2000 F. Therefore, ceramic tools can be operated 
at cutting speeds two to four times greater than 
cemented carbide tools. 

Ceramic cutting tools are available as either 
solid ceramic or as ceramic coated carbide in 
several of the insert shapes available in cemented 
carbides and are secured in the toolholder by a 
clamp. 

Whenever you handle ceramic cutting tools, 
be very careful because they are very brittle and 
will not tolerate shock or vibration. Be sure your 
lathe setup is very rigid and do not try to take any 
interrupted cuts. Also ensure that the lathe feed 
rate does not exceed 0.015 to 0.020 inch per 
revolution, as any rate exceeding this will subject 
the insert to excessive forces and may result in 
fracturing the insert. 

ENGINE LATHE TOOLS 

Figure 6-15 shows the most popular shapes 
of ground lathe tool cutter bits and their 
applications. In the following paragraphs each of 
the types shown is described. 



LEFT-HAND TURNING TOOL 

This tool is ground for machining work when 
fed from left to right, as indicated in figure 6- 15 A. 
The cutting edge is on the right side of the tool 
and the top of the tool slopes down away from 
the cutting edge. 

ROUND-NOSE TURNING TOOL 

This tool is for general all-round machine 
work and is used for taking light roughing cuts 
and finishing cuts. Usually, the top of the cutter 
bit is ground with side rake so that the tool may 
be fed from right to left. Sometimes this cutter 
bit is ground flat on top so that the tool may be 
fed in either direction (fig. 6-15B). 

RIGHT-HAND TURNING TOOL 

This is just the opposite of the left-hand 
turning tool and is designed to cut when fed from 
right to left (fig. 6-15C). The cutting edge is on 
the left side. This is an ideal tool for taking 
roughing cuts and for general all-round machine 
work. 

LEFT-HAND FACING TOOL 

This tool is intended for facing on the left- 
hand side of the work, as shown in figure 6-15D. 
The direction of feed is away from the lathe 
center. The cutting edge is on the right-hand side 
of the tool and the point of the tool is sharp to 
permit machining a square corner. 

THREADING TOOL 

The point of the threading tool is ground to 
a 60 included angle for machining V-f orm screw 
threads (fig. 6-15E). Usually, the top of the tool 
is ground flat and there is clearance on both sides 
of the tool so that it will cut on both sides. 

RIGHT-HAND FACING TOOL 

This tool is just the opposite of the left-hand 
facing tool and is intended for facing the right 
end of the work and for machining the right side 
of a shoulder. (See fig. 6-15F.) 

SQUARE-NOSED PARTING 
(CUT-OFF) TOOL 

The principal cutting edge of this tool is on 
the front. (See fig. 6-1 5G.) Both sides of the tool 




LATHE TOOLHOLDER-STRAIGHT SHANK 



CUTTER BIT-NOT GROUND 



CUTTER BIT-GROUND TO FRORM 



A 



A B C D IT F 6 

LEFT-HAND ROUND-NOSE RIGHT-HAND LEFT-HAND THREADING RIGHT-HAND CUT-OFF 
TURNING TOOL TURNING TOOL TURNING TOOL FACE ING TOOL TOOL FACING TOOL TOOL 




INSIDE 

THREADING 

TOOL 



Figure 6-15. Lathe tools and their application. 



must have sufficient clearance to prevent 
binding and should be ground slightly nar- 
rower at the back than at the cutting edge. 
This tool is convenient for machining necks, 
grooves, squaring corners, and for cutting 
off. 



BORING TOOL 

The boring tool is usually ground the san 
shape as the left-hand turning tool so that tl 
cutting edge is on the front side of the cutter b 
and may be fed in toward the headstock. 



6-17 



INTERNAL-THREADING TOOL 

The internal-threading (inside-threading) tool 
is the same as the threading tool in figure 6-1 5E, 
except that it is usually much smaller. Boring and 
internal-threading tools may require larger relief 
angles when used in small diameter holes. 



GRINDING ENGINE LATHE 
CUTTING TOOLS 

The materials being machined and the 
machining techniques used limit the angles of a 
tool bit. When grinding the angles, however, you 
must also consider the type of toolholder and the 
position of the tool with respect to the axis of the 
workpiece. The angular offset and the angular 
vertical rise of the tool seat in a standard lathe 
toolholder affect the cutting edge angle and the 
end clearance angle of a tool when it is set up for 
machining. The position of the point of the tool 
bit with respect to the axis of the workpiece, 
whether higher, lower, or on center, changes the 
amount of front clearance. 

Figure 6-16 shows some of the standard tool- 
holders used in lathe work. Notice the angles at 
which the tool bits sit in the various holders. You 
must consider these angles with respect to the 
angles ground in the tools and the angle that you 
set the toolholder with respect to the axis of the 
work. Also notice that a right-hand toolholder is 
offset to the LEFT and a left-hand toolholder 
is offset to the RIGHT. For most machining 
operations, a right-hand toolholder uses a left- 
hand turning tool and a left-hand toolholder uses 
a right-hand turning tool. Study figure 6-15 and 
6-16 carefully to clearly understand this apparent 
contradiction. (Carbide tipped cutting tools should 
be held directly in the toolpost or in heavy duty 
holders similar to those used on turret lathes.) 

The contour of a cutting tool is formed by the 
side cutting edge angle and the end cutting edge 





STRAIGHT SHANK TURNING TOOL 




angle of the tool. (Parts A through G of fig. 6-15 
illustrate the recommended contour of several 
types of tools.) There are no definite guidelines 
on either the form or the included angle of the 
contour of pointed tool bits. Each machinist 
usually forms the contour as he or she prefers. 
For roughing cuts, it is recommended that the 
included angle of the contour of pointed bits be 
made as large as possible and still provide 
clearance on the trailing side or end edge. Tools 
for threading, facing between centers, and parting 
have specific shapes because of the form of the 
machined cut or the setup used. 

STEPS IN GRINDING A TOOL BIT 

The basic steps are similar for grinding a 
single-edged tool bit for any machine. The 
difference lies in shapes and angles. Use a coolant 
when you grind tool bits. Finish the cutting edge 
by honing it on an oilstone. The basic steps for 
grinding a round nose turning tool are illustrated 
in figure 6-17. A description of each step follows: 

1 . Grind the left side of the tool, holding it 
at the correct angle against the wheel to 
form the necessary side clearance. Use the 
coarse grinding wheel to remove most of 
the metal, and then finish on the fine 
grinding wheel. (If the cutting edge is 
ground on the periphery of a wheel less 
than 6 inches in diameter, it will be under- 
cut and will not have the correct angle.) 
Keep the tool cool while grinding. 

2. Grind the right side of the tool, holding it 
at the required angle to form the right side. 

3. Grind the radius on the end of the tool. A 
small radius (approximately 1/32 inch) is 



' LEFT-HAND 
TURNING TOOL 



RIGHT-HAND 
TURNING TOOL 




::*:". CUTTER 
BIT 



Figure 6-16. Standard lathe toolholders. 



Figure 6-17. Grinding and honing a lathe cutter bit. 



preferable, as a large radius may cause 
chatter. Hold the tool lightly against the 
wheel and turn it from side to side to 
produce the desired radius. 

4. Grind the front of the tool to the desired 
front clearance angle. 

5 . Grind the top of the tool, holding it at the 
required angle to obtain the necessary side 
rake and back rake. Try not to remove too 
much of the metal. The more metal you 
leave on the tool, the better the tool will 
absorb the heat produced during cutting. 

6. Hone the cutting edge all around and on 
top with an oilstone until you have a keen 
cutting edge. Use a few drops of oil on the 
oil-stone when honing. Honing will not 
only improve the cutting quality of the tool, 
but will also produce a better finish on the 
work, and the cutting edge of the tool will 
stand up much longer than if it is not 
honed. The cutting edge should be sharp 
in order to shear off the metal instead of 
tearing it off. 

GRINDING TOOLS FOR 
ROUGHING CUTS 

A single-edged cutting tool used for roughing 
cuts (relatively heavy depth of cut and heavy feed) 
can be modified slightly and used for finishing 



operations. In finishing, lighter feed and less 
depth of cut are normally used to get a smooth 
surface. To grind a finishing tool from a roughing 
tool, it is usually necessary only to increase the 
back rake angle, decrease the side rake and side 
clearance angles, and grind a radius on the nose 
of the tool. The only portion of a tool ground in 
this manner that will be cutting is the nose. 
Grinding a larger back rake angle makes a more 
acute, chisel-type nose. Decreasing side rake and 
side clearance provides more support for the 
cutting edge. By increasing the radius of the nose, 
you ensure that more of the cutting edge will be 
in contact with the work during the cut; and thus, 
by decreasing the feed rate of the tool, you will 
have a finer cut (similar to a scraping) which 
ensures a good finish. 

In general machining work, you will find that 
it is easy to grind a tool which can be used for 
both roughing and finishing. To do this you grind 
a roughing tool to increase the nose radius a little 
more than usual. When you take the finish cut, 
decrease the feed rate until you obtain the required 
finish. 

Table 6-2 gives recommended angles for 
roughing and finishing cuts for tools made of 
various materials. The values provided in table 
6-2 are somewhat arbitrarily selected as the most 
appropriate so that you can grind a minimum 



Table 6-2. Angles for Grinding Engine Lathe Tools 



Material 


Operation 


Angle (Degrees) 


Back 
Rake 


Side 
Rake 


Side 
Relief 


End 
Relief 


Mild steel 


Roughing 
Finishing 


6-10 
14-22 


14-22 



5-9 



5-9 
5-9 


Hard steel and cast 
iron 


Roughing 
Finishing 


6-8 
6-10 


12-14 



5-9 



5-9 
5-9 


Brass and bronze 


Roughing 
Finishing 


6-8 
14-22 


4-10 



5-9 



5-9 
5-9 


Copper and aluminum 


Roughing 
Finishing 


8-10 
8 


16-24 
16-24 


5-9 



5-9 
5-9 


Monel 


Roughing 
Finishing 


4-8 
14-22 


10-14 



5-9 



5-9 
5-9 



number of tools for maximum use, with respect 
to materials commonly machined in the shop. The 
angles given in table 6-2 and other tables in this 
chapter are intended as guidelines for the 
beginner. As you gain experience, you will find 
that you can grind tools that cut efficiently even 
though the angles do not conform exactly to the 
angles prescribed. 

In table 6-2 you will note that the front 
clearance angles are practically standard for 
commonly used materials. The angle of side 
clearance within the tolerance given is based on 
the fact that small angles are necessary when a 
light feed rate is used and larger angles are 
necessary when a higher feed rate is used. The 
front clearance angle should generally be increased 
in proportion to the increase in the diameter of 
the workpiece. 

TURRET LATHE TOOLS 

The angles of cutting tools for turret lathes 
are quite similar to those for engine lathe tools. 



However, the cutters themselves are usually much 
larger than those used on an engine lathe because 
the turret lathe is designed to remove large 
quantities of metal rapidly. 

The relative merits, limitations, and applica- 
tions, as well as the grinding of carbon tool steel, 
high-speed steel, Stellite, and carbide tool bits 
have been discussed in relation to engine lathe 
tools. That information is applicable to turret 
lathe cutters, with a few exceptions which will be 
discussed here. 

The turret lathe cutter must withstand heavy 
cutting pressures; therefore, its cutting edge must 
be well supported. The amount of support 
depends upon the amount of side clearance, side 
rake, front clearance, and back rake given the 
tool. The clearance and rake angles prescribed in 
table 6-2 for tool bits are given in ranges, but a 
turret lathe cutter clearance and rake angles must 
be more specifically controlled. You must know 
the exact tool angles and grind the cutter to those 
angles. Table 6-3 lists the angles to which high- 
speed and carbon steel cutters should be ground 



Table 6-3. Angles for Grinding Turrent Lathe Tools (High Speed and Carbon Steel) 







Angle (D 


egrees) 




Material 


Side 
Clearance 


Front 
Clearance 


Back 
Rake 


Side 
Rake 


Cast Iron 


g 


g 


g 


14 


Copper 


g 


g 


in 


25 


Brass, Soft 


g 


g 


n 


n 


Hard Bronze 


g 


g 


R 


c; 


Aluniinum 


g 


Q 


g 


1 g 


Steels: 
SAE XI 112 Spec Screw Stock 


g 


g 


1 ^ 


?n 


SAE X1315 Screw Stock 


g 


g 


1 S 


on 


SAE 1020 Carbon Steel 


8 


8 


15 


15 


SAE 1035 Carbon Steel 


8 


8 


15 


15 


SAE 1045 Carbon Steel 


8 


8 


10 


12 


SAE 1095 High Carbon Steel 


8 


8 


5 


10 


SAE 2315 Nickel Alloy 


8 


8 


15 


15 


SAE 2335 Nickel Alloy (Annealed) 


8 


8 


15 


15 


SAE 2350 Nickel' Steel (Annealed) 


8 


8 


10 


12 


SAE 3115 Nickel- Chromium Alloy 


8 


8 


15 


15 


SAE 3140 Nickel- Chromium (Annealed) 
SAE 3250 Nickel -Chromium (Annealed) 
SAE 4140 Chromium-Molybdenum 
SAE 4615 Nickel -Molybdenum 
SAE 6145 Chromium- Vanadium 


8 
8 
8 
8 
8 


8 
8 
8 
8 
8 


10 
8 
10 
15 
8 


12 
12 
12 
15 
12 



6-20 



As carbide tips cannot tolerate bending but are 
otherwise capable of withstanding heavy cutting 
pressures, the tool angles prescribed for them are 
somewhat different. Table 6-4 lists the clearance 
and rake angles for carbide-tipped cutters. Notice 
that the side and front clearance angles differ only 
slightly from those prescribed for high-speed 
steel cutters but that the rake angles differ 
considerably. The reduction in back rake and side 
rake angles for carbide-tipped tools provides a 
bigger included angle for the cutting edge and, 
therefore, greater resistance against bending 
stress. 

Before a carbide tip is ground, a clearance 
angle is ground on the shank with a conventional 
grinding wheel. This clearance angle must be 
slightly larger than the angle to be ground on the 
carbide tip. The clearance prevents loading the 
grinding wheel with the soft material of the shank 
when the clearance angles are ground on the tip. 

Stellite cutters should be given tool angles 
that lie approximately midway between those 
prescribed for the high-speed steel and the carbide- 
tipped types. 



un ccuuna.1 control 101 its caips, cspciaouy 

the cutter is to machine a tough ductile metal from 
which the chip peels off in a continuous stream. 
A long, hot chip, in addition to being hazardous 
to you, will often interfere with the operation of 
the other cutters or with the operation of the lathe 
itself unless the direction of its run-off is 
controlled. As some other factors are involved, 
chip control will be discussed after the setting of 
cutters has been taken up in chapter 10. 



SHAPER AND PLANER TOOLS 

Shaper and planer cutting tools are similar in 
shape to lathe tools but differ mainly in their relief 
angles. As these cutting tools are held practically 
square with the work and do not feed during the 
cut, relief angles are much less than those required 
for turning operations. Nomenclature used for 
shaper and planer tools is the same as that for 
lathe tools; and the elements of the tool, such as 
relief and rake angles, are in the same relative 
position as shown in figure 6-13 . Both carbon and 
high-speed steel are used for these tools. 



Table 6-4. Angles for Grinding Turret Lathe Tools (Carbide) 



Material 


Angle (Degrees) 


Side 
Clearance 


Front 
Clearance 


Back 
Rake 


Side 
Rake 


Cast Iron 


4-6 


4-6 


0-4 


10-12 


Aluminum 


8-10 


8-10 


25 


15 


Copper 


8-10 


8-10 


4 


20 


Brass 


6 


6 





4 


Bronze 


6 


6 





4 


Low carbon steel up to 0.20% carbon 


8-10 


8-10 


4-6 


10-12 


Carbon steel up to . 60% carbon 


8-10 


8-10 


4-6 


10-12 


Tool steel over . 60% carbon, and tough alloys 


8-10 


8-10 


4-6 


6-10 



NOTE: Keep back rake angle as small as possible for greatest strength. 



6-21 



shaper or planer. Although the types differ 
considerably as to shape, the same general rules 
govern the grinding of each type. Hand forging 
of shaper and planer tools is a thing of the past. 
Toolholders and interchangeable tool bits have 
replaced forged tools; this practice greatly reduces 
the amount of tool steel required for each tool. 

For an efficient cutting tool, the side relief and 
end relief of the tool must be ground to give a 
projecting cutting edge. If the clearance is 
insufficient, the tool bit will rub the work, causing 
excessive heat and producing a rough surface on 
the work. If too much relief is given the tool, the 
cutting edge will be weak and will tend to break 
during the cut. The front and side clearance angles 
seldom exceed 3 to 5 . 

In addition to having relief angles, the tool bit 
must slope away from the cutting edge. This slope 
is known as side rake and reduces the power 
required to force the cutting edge into the work. 
The side rake angle is usually 10 or more, 
depending upon the type of tool and the metal 
being machined. Roughing tools are given no back 
rake although a small amount is generally required 
for finishing operations. 

The shape and use of various standard 
cutting tools are illustrated in figure 6-18 and may 
be outlined as follows: 

ROUGHING TOOL (fig. 6-1 8 A): This tool 
is very efficient for general use and is designed 




A. ROUGHING 
TOOL 



8. DOWNCUTTING TOOLS 
(RIGHT-ANO LEFT-HAND) 



C.SHOVEL NOSE 
TOOL 




0. SIDE TOOLS 
(RIGHT-ANO LEFT-HAND) 



E. CUTTING- 
OFF TOOL 



F, SQUARING 
TOOL 




G. ANGLE CUTTING TOOLS 
(RIGHT- AND LEFT-HAND) 



H- SHEAR 
TOOL 



I. GOOSENECK 
TOOL 



Figure 6-18. Standard shaper and planer tools. 



operation as illustrated; for special applications, 
the angles may be reversed for right-hand cuts. 
No back rake is given this tool although the side 
rake may be as much as 20 for soft metals. 
Finishing operations on small flat pieces may be 
performed with the roughing tool if a fine feed 
is used. 

DOWNCUTTING TOOL (fig. 6-18B): The 
downcutting tool may be ground and set for either 
right- or left-hand operation and is used for mak- 
ing vertical cuts on edges, sides, and ends. The 
tool is substantially the same as the roughing tool 
described, with the exception of its position in the 
toolholder. 

SHOVEL NOSE TOOL (fig. 6-18C): This tool 
may be used for downcutting in either a right- or 
left-hand direction. A small amount of back rake 
is required, and the cutting edge is made the widest 
part of the tool. The corners are slightly rounded 
to give them longer life. 

SIDE TOOL (fig. 6-18D): Both right- and left- 
hand side tools are required for finishing vertical 
cuts. These tools may also be used for cutting or 
finishing small horizontal shoulders after a ver- 
tical cut has been made in order to avoid chang- 
ing tools. 

CUTTING-OFF TOOL (fig. 6-18E): This tool 
is given relief on both sides to allow free cutting 
action as the depth of cut is increased. 

SQUARING TOOL (fig. 6-18F): This tool is 
similar to the cutting-off tool and may be made 
in any desired width. The squaring tool is used 
chiefly for finishing the bottom and sides of 
shoulder cuts, key ways, and grooves. 

ANGLE CUTTING TOOL (fig. 6-1 8G): The 
angle cutting tool is adapted for finishing 
operations and is generally used following a 
roughing operation made with the downcutting 
tool. The tool may be ground for eight right- or 
left-hand operation. 

SHEAR TOOL (fig. 6-18H): This tool is used 
to produce a high finish on steel and should be 
operated with a fine feed. The cutting edge is 
ground to form a radius of 3 to 4 inches, twisted 
to a 20 to 30 angle, and given a back rake in 
the form of a small radius. 



6-22 



so that the cutting edge is behind the backside of 
the tool shank. This feature allows the tool to 
spring away from the work slightly, reducing the 
tendency for gouging or chattering. The cutting 
edge is rounded at the corners and given a small 
amount of back rake. 

GRINDING HANDTOOLS 
AND DRILLS 

Tools and Their Uses, NAVEDTRA 10085 
(series), contains detailed descriptions of the off- 
hand grinding of twist drills and handtools. 
Therefore, these subjects are not discussed here. 
You should study NAVEDTRA 10085 (series) so 
that you can accurately grind these tools that you 
will often use in your work. 

WHEEL CARE AND STORAGE 

All grinding wheels can be broken or damaged 
by mishandling and improper storage. Whenever 



hard objects such as the grinder or other 
wheels. 

Grinding wheels should be stored in a 
cabinet or on shelves large enough to allow 
selection of a wheel without disturbing the 
other wheels. The storage space should pro- 
vide protection against high humidity, con- 
tact with liquids, freezing temperatures, and 
extreme temperature changes. Also, provisions 
must be made to secure grinding wheels 
aboard ship to prevent them from being 
damaged when the ship is at sea. Thin cut- 
off wheels should be stacked flat on a rigid 
surface without any separators or blotters 
between them, flaring cup wheels should be 
stacked flat with the small ends together. All 
other types of wheels may be stored upright on 
their rims with blotters placed between them. A 
sheet metal cabinet, lined with felt or corrugated 
cardboard to prevent wheel chipping, is acceptable 
for storage. 



6-23 



LATHES AND ATTACHMENTS 



There are several types of lathes installed in 
shipboard machine shops including the engine 
lathe, horizontal turret lathe, vertical turret lathe, 
and several variations of the basic engine lathe, 
such as bench, toolroom, and gap lathes. All 
lathes, except the vertical turret type, have one 
thing in common for all usual machining 
operations the workpiece is held and rotated 
around a horizontal axis while being formed to 
size and shape by a cutting tool. In a vertical 
turret lathe, the workpiece is rotated around a 
vertical axis. 

All of the lathes mentioned above, as well as 
many of their attachments, are described in 
this and the next three chapters. Engine lathe 
operations and turret lathes and their operations 
are covered later in this manual. 



ENGINE LATHE 

An engine lathe similar to the one shown in 
figure 7-1 is found in every machine shop. It is 
used mainly for turning, boring, facing, and screw 
cutting, but it may also be used for drilling, 
reaming, knurling, grinding, spinning, and spring 
winding. The work held in an engine lathe can 
be rotated at any one of a number of different 
speeds. The cutting tool can be accurately 
controlled by hand or power for longitudinal feed 
and crossfeed. (Longitudinal feed is the movement 
of the cutting tool parallel to the axis of the lathe; 
crossfeed is the movement of the cutting tool 
perpendicular to the axis of the lathe.) 

Lathe size is determined by various methods 
depending upon the manufacturer. Generally, the 
size is determined by two measurements: (1) either 
the diameter of work it will swing over the bed 
or the diameter of work it will swing over the 
cross-slide and (2) either the length of the bed or 
the maximum distance between centers. For 



example, a 14-inch x 6-foot lathe has a bed that 
is 6 feet long and will swing work (over the bed) 
up to 14 inches in diameter. 

Engine lathes range in size from small bench 
lathes with a swing of 9 inches to very large lathes 
for turning work of large diameters, such as low- 
pressure turbine rotors. A 16-inch swing lathe is 
a good, average size for general purposes and is 
usually the size installed in ships that have only 
one lathe. 

To learn the operation of a lathe, you must 
be familiar with the names and functions of the 
principal parts. In studying the principal parts in 
detail, remember that lathes all provide the same 
general functions even though the design may 
differ among manufacturers. As you read the 
description of each part, find its location on the 
lathe pictured in figure 7-1. For specific details 
on a given lathe, refer to the manufacturer's 
technical manual for that machine. 



BED AND WAYS 

The bed is the base for the working parts of 
the lathe. The main feature of the bed is the ways, 
which are formed on its upper surface and run 
the full length of the bed. The tailstock and 
carriage slide on the ways in alignment with the 
headstock. The headstock is permanently bolted 
to the end at the operator's left. 

Figure 7-2 shows the ways of a typical lathe. 
The inset shows the inverted V-shaped ways 
(1,3, and 4) and the flat way (2). The ways are 
accurately machined parallel to the axis of the 
spindle and to each other. The V-ways are guides 
that allow the carriage and tailstock to move over 
them only in their longitudinal direction. The flat 
way, number 2, takes most of the downward 
thrust. The carriage slides on the outboard V-ways 
(1 and 4), which, because they are parallel to way 



7-1 



"' ;; ?""-:"--:" j. 1 , r----i\& '"' '--- ' ; lli|$ 



33 32 31 3 ,29 

/ / _/ / 












18 19 



1. Headstock spindle 

2. Identification plate 

3. Spindle speed index plate 

4. Headstock spindle speed change 

levers 

5. Upper compound lever 

6. Lower compound lever 

7. Tumbler lever 

8. Feed-thread index plate 

9. Feed-thread lever 

10. Spindle control lever 

11. Electrical switch grouping 

12. Apron handwheel 

13. Longitudinal friction lever 

14. Cross-feed friction lever 

15. Feed directional control lever 

16. Half nut closure lever 



17. Spindle control lever 

18. Leadscrew reverse lever 

19. Reverse rod stop dog 

20. Control rod 

21. Feed rod 

22. Lead screw 

23. Reverse rod 

24. Tailstock setover screw 

25. Tailstock handwheel 

26. Tailstock clamping lever 

27. Tailstock spindle binder lever 

28. Tailstock spindle 

29. Chasing dial 

30. Carriage binder clamp 

31. Compound rest dial and handle 

32. Thread chasing stop 

33. Cross-feed dial and handle 



28.69X 



Figure 7-1. Gear-head engine lathe. 



7-2 




28.70X 



Figure 7-2. Rear view of lathe. 



number 3, keep the carriage aligned with the 
headstock and the tailstock at all times an 
absolute necessity if accurate lathe work is to be 
done. Some lathe beds have two V-ways and two 
flat ways, while others have four V-ways. 

For a lathe to perform satisfactorily, the ways 
must be kept in good condition. A common fault 
of careless machinists is to use the bed as an 
anvil for driving arbors or as a shelf for hammers, 
wrenches, and chucks. Never allow anything to 
strike a hard blow on the ways or damage their 
finished surfaces in any way. Keep them clean 
and free of chips. Wipe them off daily with 
an oiled rag to help preserve their polished 
surface. 



HEADSTOCK 

The headstock carries the headstock spindle 
and the mechanism for driving it. In the 
belt-driven type the driving mechanism con- 
sists merely of a cone pulley that drives 
the spindle directly or through back gears. 
When the spindle is driven directly, it rotates 
with the cone pulley; when the spindle is 
driven through the back gears, it rotates 
more slowly than the cone pulley, which in 
this case turns freely on the spindle. Thus 
two speeds are available with each position 
of the belt on the cone; if the cone pulley 
has four steps, eight spindle speeds are avail- 
able. 



7-3 



The geared headstock shown in figure 7-3 is 
more complicated but more convenient to operate 
because speed is changed by shifting gears. 
This headstock is similar to an automobile 
transmission except that it has more gear-shift 
combinations and therefore has a greater number 
of speed changes. A speed index plate, attached 
to the headstock, shows the lever positions for the 
different spindle speeds. Figure 7-4 shows this 
plate for the geared headstock in figure 7-3. 
Always stop the lathe when you shift gears to 
avoid damaging the gear teeth. 

Figure 7-3 shows the interior of a typical 
geared headstock that has 16 different spindle 
speeds. The driving pulley at the left is driven at 
a constant speed by a motor located under the 
headstock. Various combinations of gears in the 
headstock transmit the power from the drive shaft 
to the spindle through an intermediate shaft. Use 
the speed-change levers to shift the sliding gears 
on the drive and intermediate shafts to line up the 
gears in different combinations. This produces the 
gear ratios you need to obtain the various spindle 
speeds. Note that the back gear lever has high and 
low speed positions for each combination of the 
other gears (figure 7-4). 




PULLEY 500 RPM 



CONTRACT No.. 

DATf Of 
UAJWMCTUM 



vw 



16 



19 



26 



42 



52 



65 



81 



98 



121 



152 



Z46 



305 



385 



76 



28.73 



Figure 7-4. Speed index plate. 



The headstock casing is filled with oil to 
lubricate the gears and the shifting mechanism it 
contains. Parts not immersed in the oil are 
lubricated by either the splash produced by the 
revolving gears or by an oil pump. Be sure to keep 
the oil to the oil level indicated on the oil gauge, 
and drain and replace the oil when it becomes 
dirty or gummy. 

The headstock spindle (fig. 7-5) is the main 
rotating element of the lathe and is directly 
connected to the work, which revolves with it. The 
spindle is supported in bearings (4) at each end 




28.72 




28.74X 
Figure 7-5. Cross section of a belt-driven headstock. 



of the headstock through which it projects. The 
section of the spindle between the bearings 
carries the pulleys or gears that turn the spindle. 
The nose of the spindle holds the driving plate, 
the faceplate, or a chuck. The spindle is hollow 
throughout its length so that bars or rods can be 
passed through it from the left (1) and held in a 
chuck at the nose. The chuck end of the spindle 
(5) is bored to a Morse taper to receive the LIVE 
center. The hollow spindle also permits the use 



j uy wijuc.ii uiv opinviiv VJ.AIVVO tiiw j.i*vu 

and screw-cutting mechanism through a gear train 
located on the left end of the lathe. A collar (3) 
is used to adjust end play of the spindle. 

The spindle is subjected to considerable torque 
because it both drives the work against the 
resistance of the cutting tool and drives the 
carriage that feeds the tool into the work. For this 
reason adequate lubrication and accurately 
adjusted bearings are absolutely necessary. (Bear- 
ing adjustment should be done only by an 
experienced lathe repairman.) 

TAILSTOCK 

The primary purpose of the tailstock (fig. 7-6) 
is to hold the DEAD or LIVE center to support 
one end of work being machined on centers. 
However, it can also be used to hold tapered 
shank drills, reamers, and drill chucks. The 
tailstock moves on the ways along the length of 
the bed to accommodate work of varying lengths. 




Nlft \L1 



1. Tailstock base. 9. 

2. Tailstock top. 10. 

3. Tailstock nut. 11. 

4. Key. 12. 

5. Keyway (in spindle). 13. 

6. Spindle. 14. 

7. Tailstock screw. 15. 

8. Internal threads in spindle. 16. 



Handwheel. 

Spindle binding clamp. 

Dead center. 

End of tailstock screw. 

Tailstock clamp nut. 

Tailstock set-over. 

For oiling. 

Tailstock clamp bolt. 



Figure 7-6. Cross section of a tailstock. 



28.75X 



7-5 



It can be clamped in the desired position by the 
tailstock clamping nut (13). 

The dead center (1 1) is held in a tapered hole 
(bored to a Morse taper) in the tailstock 
spindle (6). To move the spindle back and forth 
in the tailstock barrel for longitudinal adjustment, 
turn the handwheel (9) which turns the spindle- 
adjusting screw (7) in a tapped hole in the spindle 
at (8). The spindle is kept from revolving by a key 
(4) that fits a spline, or key way, (5) cut along the 
bottom of the spindle as shown. After making the 
final adjustment, use the binding clamp (10) to 
lock the spindle in place. 

The tailstock body is made in two parts. The 
bottom, or base (1), is fitted to the ways; the top 
(2) can move laterally on its base. The lateral 
movement can be closely adjusted by setscrews. 
Zero marks inscribed on the base and top indicate 
the center position and provide a way to measure 
setover for taper turning. Setover of the tailstock 
for taper turning is described in a later chapter. 

Before you insert a dead center, a drill, or a 
reamer into the spindle, carefully clean the tapered 
shank and wipe out the tapered hole of the 
spindle. After you put a drill or a reamer into the 



tapered hole of the spindle, be sure to tighten i 
in the spindle so that the tool will not revolve. I 
the drill or reamer is allowed to revolve, it wil 
score the tapered hole and destroy its accuracy 
The spindle of the tailstock is engraved witl 
graduations which help in determining the deptl 
of a cut when you drill or ream. 

CARRIAGE 

The carriage carries the crossfeed slide and th 
compound rest which in turn carries the cuttinj 
tool in the toolpost. The carriage slides on th 
ways along the bed (fig. 7-7). 

Figure 7-8 shows a top view of the carriage 
The wings of the H-shaped saddle contain tin 
bearing surfaces which are fitted to the V-way 
of the bed. The crosspiece is machined to forn 
a dovetail for the crossfeed slide. The crossfee< 
slide is closely fitted to the dovetail and has ; 
tapered gib which fits between the carriage 
dovetail and the matching dovetail of th 
crossfeed slide. The gib permits small adjustment 
to remove any looseness between the two parts 
The slide is securely bolted to the crossfeed nu 



COMPOUND REST 



CROSS-SLIDE 



CARRIAGE 




WAYS 



BED 



28.7 



CROSS SECTION AT X.X TO SHOW 

DOVETAIL FOR CROSS-SLIDE AND 

RECESS FOR CROSSFEED NUT X 




MICROMETER DIAL 
CROSSFEED HANDLE 



28.77X 



Figure 7-8. Carriage (top view). 



which moves back and forth when the crossfeed 
screw is turned by the handle. The micrometer dial 
on the crossfeed handle is graduated to permit 
accurate infeed. Depending on the manufacturer 
of the lathe, the dial may be graduated 
so that each division represents a 1 to 1 or a 2 to 
1 ratio. The compound rest is mounted on top 
of the crossfeed slide. 

The carriage has T-slots or tapped holes for 
clamping work for boring or milling. When the 
lathe is used in this manner, the carriage move- 
ment feeds the work to the cutting tool which is 
revolved by the headstock spindle. 

You can lock the carriage in any position on 
the bed by tightening the carriage clamp screw. 
Use the clamp screw only when doing such work 
as facing or cutting-off for which longitudinal 
feed is not required. Normally, keep the carriage 
clamp in the released position. Always move the 
carriage by hand to be sure it is free before you 
apply the automatic feed. 

APRON 

The apron is attached to the front of the 
carriage. It contains the mechanism that controls 
the movement of the carriage for longitudinal feed 
and thread cutting and controls the lateral move- 
ment of the cross-slide. You should thoroughly 



a mine ctpiuu wumcuus uic iuuu vy- 
ing mechanical parts: 

1. A longitudinal feed HANDWHEEL for 

moving the carriage by hand along the bed. 
This handwheel turns a pinion that meshes 
with a rack gear secured to the lathe bed. 

2. GEAR TRAINS driven by the feed rod. 
These gear trains transmit power from the 
feed rod to move the carriage along the 
ways and to move the cross-slide across the 
ways, thus providing powered longitudinal 
feed and crossfeed. 

3. FRICTION CLUTCHES operated by 
knobs on the apron to engage or disengage 
the power- feed mechanism. (Some lathes 
have a separate clutch for longitudinal feed 
and crossfeed; others have a single clutch 
for both.) NOTE: The power feeds are 
usually driven through a friction clutch to 
prevent damage to the gears if excessive 
strain is put on the feed mechanism. If 
clutches are not provided, there is some 
form of safety device that operates to 
disconnect the feed rod from its driving 
mechanism. 

4. A selective FEED LEVER or knob for 
engaging the longitudinal feed or crossfeed 
as desired. 

5. HALF-NUTS that engage and disengage 
the lead screw when the lathe is used to cut 
threads. They are opened or closed by a 
lever located on the right side of the apron. 
The half-nuts fit the thread of the lead 
screw which turns in them like a bolt in a 
nut when they are clamped over it. The 
carriage is then moved by the thread of the 
lead screw instead of by the gears of the 
apron feed mechanisms. (The half -nuts are 
engaged only when the lathe is used to cut 
threads, at which time the feed mechanism 
must be disengaged. An interlocking device 
that prevents the half-nuts and the feed 
mechanism from engaging at the same time 
is usually provided as a safety feature.) 

Aprons on lathes made by different manu- 
facturers differ somewhat in construction and in 
the location of controlling levers and knobs. 
But they all are designed to perform the same 
functions. The principal difference is in the 
arrangement of the gear trains for driving the 
automatic feeds. For example, in some aprons 



7-7 



there are two separate gear trains with separate 
operating levers for longitudinal feed and cross 
feed. In others, both feeds are driven from the 
same driving gear on the feed rod through a 
common clutch, with one feed at a time connected 
to the drive by a selector lever. The apron shown 
in figure 7-9 is of the latter type. 



FEED ROD 

The feed rod transmits power to the apron to 
drive the longitudinal feed and cross feed 
mechanisms. The feed rod is driven by the spindle 
through a train of gears, and the ratio of its speed 
to that of the spindle can be varied by changing 
gears to produce various rates of feed. The 
rotating feed rod drives gears in the apron. 
These gears in turn drive the longitudinal 
feed and crossfeed mechanisms through friction 
clutches, as explained in the description of the 
apron. 

Lathes which do not have a separate feed rod 
have spline in the lead screw to serve the same 
purpose. The apron shown in figure 7-9 belongs 
to a lathe of this type and shows clearly how the 
worm which drives the feed mechanism is driven 
by the spline in the lead screw. If a separate feed 
rod were used, it would drive the feed worm in 
the same manner, that is, by means of a spline. 
The spline permits the worm, which is keyed to 
it, to slide freely along its length to conform with 
the movement of the carriage apron. 



LEAD SCREW 

The lead screw is used for thread cutting. 
Along its length are accurately cut Acme threads 
which engage the threads of the half-nuts in the 
apron when half -nuts are clamped over it. When 
the lead screw turns in the closed half -nuts, the 
carriage moves along the ways a distance equal 
to the lead of the thread in each revolution of the 
lead screw. Since the lead screw is connected to 
the spindle through a gear train (discussed later 
in the section on quick-change gear mechanism), 
the lead screw rotates with the spindle. There- 
fore, whenever the half -nuts are engaged, the 
longitudinal movement of the carriage is directly 
controlled by the spindle rotation. The cutting tool 
is moved a definite distance along the work for 
each revolution that the spindle makes. 

The ratio of the threads per inch of the thread 
being cut and the thread of the lead screw is the 
same as the ratio of the speeds of the spindle and 
the lead screw. For example: If the lead screw and 
spindle turn at the same speed, the number of 
threads per inch being cut is the same as the 
number of threads per inch of the lead screw. 
If the spindle turns twice as fast as the lead 
screw, the number of threads being cut is twice 
the number of threads per inch of the lead 
screw. 

You can cut any number of threads by merely 
changing gears in the connecting gear train to 
get the desired ratio of spindle and lead screw 
speeds. 




28.79X 



Figure 7-9. Rear view of a lathe apron. 



GEARING 

First, consider the simplest possible arrange- 
ment of gearing between the spindle and the lead 
screw a gear on the end of the spindle meshed 
with a gear on the end of the lead screw, as shown 
in figure 7-10. Let a be point of contact between 
the spindle gear A and the screw gear B. As each 
tooth on gear A passes point a, it causes a tooth 
on gear B to pass this same point. Suppose gear 
A has 20 teeth and gear B has 40 teeth. Then when 
A makes one complete turn, 20 teeth will have 
passed point a. Since B has 40 teeth around its 
rim, only half of them will have passed point 
a. Gear B has made just one-half of a revolution 
while gear A has made one revolution. In other 
words, gear B with 40 teeth will turn half as fast 
as gear A with 20 teeth, or \heir speeds are 



7-8 




28.81X 



Figure 7-10. A simple gear arrangement. 



inversely proportional to their size. The relation 
may be expressed as follows: 

rpm of B _ number of teeth on A 
rpm of A number of teeth on B 



By now you should have discovered that the 
ratio in threads per inch of the thread to be cut 
and the lead screw is identical to the ratio of the 
number of teeth of the change gears. If the spindle 
gear is smaller than the screw gear, the thread cut 
will be finer (more threads per inch) than the lead 
screw and vise versa. 

Idler Gears 

It is obviously impracticable to have the 
spindle gear mesh directly with the screw gear 
because, for one thing, the distance between them 
is so great that the gears required would be too 
large. Therefore, smaller gears of the desired ratio 
are used, and idler gears bridge the gap between 
them. You can place any number of idler gears 
between the driving gear and the driven gear 
without changing the original gear ratio. The idler 
gears allow the lead screw and spindle gears to 
rotate as if they were in direct contact. 

In figure 7-11, I is an idler gear inserted 
between the driving gear A and the driven gear B. 



or 



rpm of lead screw _ number of teeth on spindle gear A 
rpm of spindle number of teeth on screw gear B 

By using this formula, you can change the speed 
of the screw relative to that of the spindle by 
changing the gears to get the desired ratio. 

In figure 7-10, the ratio is 20:40 or 1:2. Any 
combination of gears that has a ratio of 1 :2, such 
as 30 and 60 or 35 and 70, will cause the lead screw 
to turn half as fast as the spindle. 

Suppose you want to cut 8 threads per inch 
on a lathe that has a lead screw with 6 threads 
per inch. The carriage must carry the thread- 
cutting tool 1 inch along the work while the work 
makes eight complete revolutions. Since the lead 
screw has 6 threads per inch, it must revolve six 
times in the half-nuts to move the carriage 1 inch. 
Therefore, you must gear the lathe to cause the 
lead screw to make six revolutions while the 
spindle makes eight revolutions. In other words, 
the lead screw must turn 6/8 or 3/4 as fast as the 
spindle. Since the speeds will be proportional to 
the size of the gears, you can use any two gears 
having this ratio, such as 30 and 40, 33 and 44, 




28.82X 

Figure 7-11. Idler gear inserted between a driving gear and 
a driven gear. 



7-9 



Suppose that A has 20 teeth. In making one 
complete revolution, all of these 20 teeth will pass 
a given point a and cause 20 teeth on I to pass 
this same point. If 20 teeth on I pass point 
a, an equal number of teeth on I will pass point 
b where gear B meshes with it. Gear B will be 
moved the same distance as it would if it were 
directly meshed with A; so the ratio between their 
speeds remains the same, but the direction of 
rotation of B is reversed. Idler gears, then, are 
used for two purposes: (1) to connect gears in a 
gear train and (2) to reverse the direction of 
rotation of a gear-driven mechanism. 

Figure 7-12 is an example of simple gearing 
used on a change gear lathe. The gear on the 
spindle drives the stud gear shaft A at a fixed 
ratio, usually 1 : 1 , in which the stud gear revolves 
at the same speed as the spindle. Between the 
spindle and the stud are the idler gears X and Y 
mounted on the movable bracket controlled by 
the reverse lever. When this lever is in the down 
position, both X and Y are connected in the gear 
train as shown, and the stud shaft revolves in a 
direction opposite to that of the spindle; when the 
lever is raised, gear X is disengaged from the train, 
and gear Y is meshed directly between the spindle 
and the stud, thereby reversing the previous 
direction of the stud gear and all the gears that 
follow it. NOTE: The reverse lever has a neutral 
position that disconnects the spindle from the gear 
train. 

The lathe shown in figure 7-12 has per- 
manently mounted spindle and idler gears 



(X and Y). To vary the thread cutting gear ratios, 
you must change the stud gear and the screw gear. 
You can determine which gears on your machine 
must be changed by reading the lathe's operating 
instructions. 

A simple rule to follow in determining what 
stud and screw gears to use is: Multiply the desired 
number of threads per inch and the number of 
threads per inch in the lead screw by the same 
number; if the products correspond to the number 
of teeth in any two of the change gears at hand, 
use those gears; if not, use some other multiplier 
that will give products to match the gears 
available. For example, if you want to cut a screw 
containing 16 threads per inch on the lathe with 
a lead screw that has 6 threads per inch, use 5 for 
a multiplier: 

5 x 16 = 80 
5 x 6 = 30 

If gears with 80 teeth and 30 teeth are on hand, 
use the 30-tooth gear as the stud gear and the 
80-tooth gear as the screw gear. If you do not have 
those gears, try other multipliers until you arrive 
at a combination corresponding to gears that you 
do have. 

If you cannot get the proper ratio of gears with 
the change gears you have at hand or if the gears 
would be too small or too large to connect 
properly or conveniently (as would be the case if 




28.83X 



Figure 7-12. Simple gearing on a lathe. 



substituting two gears for an intermediate gear. 
Compounding changes the ratio of the gear train 
by the same ratio that the compounding gears bear 
to each other. 

Figure 7-13 shows a compound gear train on 
a change gear lathe. The only way it differs from 
the simple gear train (fig. 7-12) is that two extra 
gears rotating as one on a common axis are 
installed in the train following the stud gear. 
Compounding gears for a lathe usually have a 
ratio of 2 to 1 ; they double the ratio that would 
exist if simple gearing were used. 

If a 2:1 compound gear is installed in the 
manner shown in figure 7-13, the speed 
transmitted by the stud gear to the large 
compound gear is reduced by half when it is 
retransmitted by the small compound gear to the 
gears that follow. It amounts to the same thing 
as using a stud gear with half as many teeth. 

The advantage of compounding is best 
demonstrated by the following example: 

Suppose a gear ratio of 10 to 1 is required to 
cut a certain fine thread, and the smallest gear 
you have that will fit the stud has 20 teeth. You 
would need a screw gear with 200 teeth, but 
such a gear is far too large. However, by 
using a 2:1 compound gear in the manner 



Quick-Change Gear Mechanism 

To do away with the inconvenience and loss 
of time involved in removing and replacing change 
gears, most modern lathes have a self-contained 
change gear mechanism, commonly called the 
QUICK-CHANGE GEAR BOX. There are a 
number of types used on different lathes but they 
are all similar in principle. 

The mechanism consists of a cone-shaped 
group of change gears. You can instantly connect 
any single gear to the gear train by moving a 
sliding tumbler gear controlled by a lever. The 
cone of gears is keyed to a shaft which drives the 
lead screw (or feed rod) directly or through an 
intermediate shaft. Each gear in the cluster has 
a different number of teeth and hence produces 
a different gear ratio when connected in the train. 
The same thing happens as when the screw gear 
in the gear train is changed, described previously. 
Sliding gears also produce other changes in the 
gear train to increase the number of different 
ratios you can get with the cone of change gears 
described above. All changes are made by shifting 
appropriate levers Or knobs. An index plate or 
chart mounted on the gear box indicates the 
position for placing the levers to get the necessary 
gear ratio to cut the thread or produce the feed 
desired. 




LARGE 

COMPOUND 
GEAR 



SMALL 

COMPOUND 

GEAR 



28.84X 



Figure 7-13. Compound gearing on a lathe. 



7-11 



Figure 7-14 is the rear view of one type of gear 
box, showing the arrangement of gears. The 
splined shaft F turns with gear G, which is driven 
by the spindle through the main gear train on the 
end of the lathe. Shaft F in turn drives shaft H 
through the tumbler gear T which can be engaged 
with any one of the cluster of eight different size 
gears on shaft H by means of the lever C. Shaft 
H drives shaft J through a double clutch gear, 
which takes the drive through one of three gears, 
depending on the position of lever B (right, center, 
or left). Shaft J drives the lead screw through 
gear L. 

Either the lead screw or the feed rod can be 
connected to the final driveshaft of the gear box 
by engaging appropriate gears. 

Twenty-four different gear ratios are pro- 
vided by the quick-change gear box shown in 
figure 7-15. The lower lever has eight positions, 
each of which places a different gear in the 
gear train and hence produces eight different 
gear ratios. The three positions of the upper 
level produce three different gear ratios for 
each of the 8 changes obtained with the lower 
lever, thus making 24 combinations in the 
box alone. You can double this range by 
using a sliding compound gear which provides 



a high- and low-gear ratio in the main gear 
train. This gives two ratios for every combina- 
tion obtainable in the box, or 48 combinations 
in all. 

Figure 7-16 shows how the sliding compound 
gear produces two different gear ratios when it 
is moved in or out. The wide gear at the bottom 
corresponds to gear G in figure 7-14. 

INSTRUCTIONS FOR OPERATION. If 

you are to cut 16 threads per inch, locate the 
number 16 on the index plate in the first column 
and fourth line under SCREW THREADS PER 
INCH (fig. 7-15). Adjust the sliding gear knob 
(fig. 7-16) to the OUT position as indicated 
opposite 16 in the first column at the left 
(fig. 7-15). (You must stop the lathe to adjust the 
sliding gear.) Start the lathe and set top lever B 
(fig. 7-14) to the LEFT position as indicated in 
the second column, opposite 16 (fig. 7-15). 

With the lathe running, shift the tumble lever 
C to the position directly under the column in 
which 16 is located; rock it until the gears mesh 
and the handle plunger latches in the hole pro- 
vided. The lathe is now set to cut the desired 
thread if the half-nuts are clamped onto the lead 
screw. 




28.85X 




28.87X 



Figure 7-15. Quick-change gear box. 



SLIDING GEAR 
KNOB 




SLIDING GEAR- 

"OUT" POSITION 



SLIDING GEAR 

-IN" POSITION 



DRIVE SHAFT TO 
QUICK-CHANGE GEAR BOX 



28.86X 

Figure 7-16. Showing how the gear ratio is changed by 
sliding gear. 



ADJUSTING THE GEAR BOX FOR 
POWER FEEDS. The index chart on the gear 
box also shows the various rates of power 
longitudinal feed per spindle revolution that 
you can get by using the feed mechanism of the 
apron. For example, in figure 7-15, note that 
the finest longitudinal feed is 0.0030 inch per 
revolution of spindle, the next finest is 0.0032 
inch, and so on. To arrange the gear box for 
power longitudinal feed, select the feed you wish 
to use and follow the same procedure explained 
for cutting screw threads, except that you 
engage the power feed lever instead of the 
half -nuts. Crossfeeds are not listed on the chart 
but you can determine them by multiplying the 
longitudinal feeds by 0.375, as noted on the 
index plate. 

On a lathe with a separate feed rod, a feed- 
thread shifting lever located at the gear box 
(part 9 in fig. 7-1) connects the drive to the feed 
rod or the lead screw as desired. When the feed 
rod is engaged, the lead screw is disengaged and 
vice versa. 



7-13 



10- 



16 



14 




8 


1 ^ 




i 


t 


1 

^** 

V. 


*\ 
"i i 


, \\ '< 


-- 1 i. - 


tf T 


r 



40 6 JO t 




1. Cross-slide. 

2. Compound rest swivel. 

3. Compound rest top. 

4. Compound rest nut. 

5. Compound rest feed 

screw handle. 



6. Crossfeed nut. 

7. Chip guard. 

8. Swivel securing 

bolts. 

9. Toolpost. 

10. Toolpost setscrew. 



Figure 7-17. Compound rest. 



11. Toolpost wedge. 

12. Toolpost ring. 

13. Toolholder. 

14. Cutting tool. 

15. Micrometer collar. 

16. Toolholder setscrew. 




LOCKING NUT 



BORING BAR 
TOOLHOLDER 



TOOL POST 



28.88X 



28.299 



Figure 7-18. Castle type toolpost and toolholder. 



7-14 



me ieaa screw to me spmaie gear tram mat 
provides the correct conversion ratio. You can 
find information on this in handbooks for 
machinists, in the equipment technical manual, 
and through direct correspondence with the equip- 
ment manufacturer. 



COMPOUND REST 

The compound rest provides a rigid, adjust- 
able mounting for the cutting tool. The compound 
rest assembly has the following principal parts 
(fig. 7-17): 

1 . The compound rest SWIVEL (2) which can 
be swung around to any desired angle and 
clamped in position. It is graduated over 
an arc of 90 on each side of its center 
position for ease in setting to the angle you 
select. This feature is used in machining 
short, steep tapers such as the angle on 
bevel gears, valve disks, and lathe centers. 

2. The compound rest TOP, or TOPSLIDE 
(3), is mounted as shown on the swivel 
section (2) on a dovetailed slide. It is moved 
along the slide by the compound rest feed 
screw turning in nut (4), operated by handle 
(5), in a manner similar to the cross feed 
described previously (fig. 7-8). This 
provides for feeding at any angle (deter- 
mined by the angular setting of the swivel 
section), while the cross-slide feed provides 
only for feeding at a right angle to the axis 
of the lathe. The graduated collar on the 
compound rest feed screw reads in 
thousandths of an inch for fine adjustment 
in regulating the depth of cut. 



ATTACHMENTS AND 
ACCESSORIES 

Accessories are the tools and equipment 
used in routine lathe machining operations. 
Attachments are special fixtures which may be 
secured to the lathe to extend the versatility of 
the lathe to include taper-cutting, milling, and 
grinding. Some of the common accessories and 
attachments used on lathes are described in the 
following paragraphs. 



quick change are discussed in the following 
paragraphs. The sole purpose of the toolpost is 
to provide a rigid support for the toolholder. 

The standard toolpost is mounted in the 
T-slot of the compound rest top as shown in 
figure 7-17. A toolholder (13) is inserted in the 
slot in the toolpost and rests on the toolpost wedge 
(11) and the toolpost ring (12). By tightening 
setscrew (10), you clamp the whole unit firmly in 
place with the tool in the desired position. 

The castle type toolpost (fig. 7-18) is used with 
boring bar type toolholders. It mounts in the 
T-slot and the toolholder (boring bar) passes 
through it and the holddown bolt. By tightening 
the locking nut, you clamp the entire unit firmly 
in place. Various size holes through the toolpost 
allow the use of assorted diameter boring bars. 

The quick change type toolpost (fig. 7-19) is 
available in many Navy machine shops. It mounts 
in the T-slots and is tightened in place by the 
locknut, which clamps the toolpost firmly in 
place. Special type toolholders are used in 
conjunction with this type of toolpost and are held 
in place by a locking plunger which is operated 
by the toolholder locking handle. Some toolposts 
have a sliding gib to lock the toolholder. With this 
type of toolpost, only the toolholders are changed, 
allowing the toolpost to remain firmly in place, 




28.300 



Figure 7-19. Quick change toolpost. 



7-15 



TOOLHOLDERS 

Lathe toolholders are designed to be used with 
the various types of toolposts. Only the three most 
commonly used types standard, boring bar, and 
quick change are discussed in this chapter. The 
toolholder holds the cutting tool (toolbit) in a rigid 
and stable position. Toolholders are generally 
made of a softer material than the cutting tool. 
They are large in size and help to carry the heat 
generated by the cutting action away from the 
point of the cutting tool. 




STRAIGHT SHANK TURNING TOOL 






BORING TOOL 



LEFT HAND 
TURNING TOOL 




RIGHT HAND 
TURNING TOOL 



STRAIGHT CUT-OFF TOOL 



28.67 



Standard toolholders were discussed briefly in 
chapter 6 of this manual. However, there are more 
types (fig. 7-20) than those discussed in chapter 
6. Two that differ slightly from others are 
the threading and knurling toolholders. (See 
fig. 7-21.) 

The THREADING TOOL shown in figure 
7-21 has a formed cutter which needs to be ground 
on the top surface only for sharpening, the thread 
form being accurately shaped over a large arc of 
the tool. As the surface is worn away by grinding, 
you can rotate the cutter to the correct cutting 
position and secure it there by the setscrew. 
NOTE: The threading tool is not commonly used. 
It is customary to use a regular toolholder with 
an ordinary tool bit ground to the form of the 
thread desired. 

A KNURLING TOOL (fig. 7-21) carries 
pattern on the work by being fed into the work 
as it revolves. The purpose of knurling is to give 



DIAMOND 
PATTERN 



STRAIGHT 
PATTERN 



Figure 7-20. Standard lathe toolholders. 





KNURLING TOOL 




THREADING TOOL 




COARSE MEDIUM FINE COARSE MEDIUM FINE 



: i 






' 




KNURLING PRODUCED BY KNURLING PRODUCED BY 

PAIRS OF RIGHT AND PAIRS OF STRAIGHT 

LEFT-HAND STANDARD LINE KNURLS 
FACE KNURLS 



28.67 



Figure 7-21. Knurling and threading tools. 



28.301 



Figure 7-22. Types of knurling rollers. 



knurled roller comes in a wide variety of patterns. 
(See fig. 7-22.) 

The BORING BAR toolholder is nothing 
more than a piece of round stock with a screw-on 
cap. (See fig. 7-18.) The caps are available with 
square holes broached through them at various 
angles (fig. 7-18) and sizes. When the proper size 
toolbit is inserted into the cap and the cap is 
screwed on to the threaded end of the piece of 
round stock, the entire unit becomes a very rigid 
boring tool which is used with the castle type 
toolpost. 

The QUICK CHANGE toolholder (fig. 7-23) 
is mounted on the toolpost by sliding it from 




28.302 
Figure 7-23. Quick change toolpost and toolholder. 



MORSE TAPER 




PLAIN TOOLBIT THREADING PARTING 



kVSVJUlVAlllV.L 110.3 a H^lgliL aUJUOllllg HAAg LV^ ,J.iV TI _j vw. 

to set the proper height prior to locking it in place. 
The quick change toolholder comes in a wide 
range of styles. A few of these styles are shown 
in figure 7-24. 



LATHE CHUCKS 

The lathe chuck is a device for holding lathe 
work. It is mounted on the nose of the spindle. 
The work is held by jaws which can be moved in 
radial slots toward the center to clamp down on 
the sides of the work. These jaws are moved in 
and out by screws turned by a chuck wrench 
applied to the sockets located at the outer ends 
of the slots. 

The 4-JAW INDEPENDENT lathe chuck, 
figure 7-25, is the most practical for general work. 
The four jaws are adjusted one at a time, making 
it possible to hold work of various shapes and to 
adjust the center of the work to coincide with the 
axial center of the spindle. 

There are several different styles of jaws for 
4-jaw chucks. You can remove some of the chuck 
jaws by turning the adjusting screw and then 
re-inserting them in the opposite direction. Some 
chucks have two sets of jaws, one set being the 
reverse of the other. Another style has jaws that 
are bolted onto a slide by two socket-head bolts. 
On this style you can reverse the jaws by 




28.303 



Figure 7-24. Quick change toolholder. 



28.304 



Figure 7-25. Four-jaw independent chuck. 



7-17 



removing the bolts, reversing the jaws, and 
re-inserting the bolts. You can make special 
jaws for this style chuck in the shop and 
machine them to fit a particular size OD or 
ID. 

The 3-JAW UNIVERSAL or scroll chuck 
(fig. 7-26) can be used only for holding round or 
hexagonal work. All three jaws move in and out 
together in one operation. They move 
simultaneously to bring the work on center 
automatically. This chuck is easier to operate than 
the four-jaw type, but when its parts become worn 
you cannot rely on its accuracy in centering. 
Proper lubrication and constant care in use are 
necessary to ensure reliability. The same styles of 
jaws available for the 4-jaw chuck are also 
available for the 3 -jaw chuck. 

COMBINATION CHUCKS are universal 
chucks that have independent movement of each 
jaw in addition to the universal movement. 

Figures 7-3 and 7-5 illustrate the usual means 
provided for attaching chucks and faceplate to 
lathes. The tapered nose spindle (fig. 7-3) is 
usually found on lathes that have a swing greater 
than 12 inches. Matching internal tapers and 
keyways in chucks for these lathes ensure accurate 
alignment and radial locking. A free turning, 
internally threaded collar on the spindle screws 
onto a boss on the back of the chuck to secure 
the chuck to the spindle nose. On small lathes, 
chucks are screwed directly onto the threaded 
spindle nose. (See fig. 7-5.) 




The DRAW-IN COLLET chuck is used to 
hold small work for machining. It is the most 
accurate type of chuck and is intended for preci- 
sion work. 

Figure 7-27 shows the 5 parts of the collet 
chuck assembled in place in the lathe spindle. The 
collet, which holds the work, is a split cylinder 
with an outside taper that fits into the tapered 
closing sleeve and screws into the threaded end 
of the hollow drawbar that passes through the 
hollow spindle. When the handwheel, which is 
attached by threads to the outside of the drawbar, 
is turned clockwise, the drawbar pulls the collet 
into the tapered sleeve, thereby decreasing the 
diameter of the hole in the collet. As the collet 
is closed around the work, the work is centered 
accurately and is held firmly by the chuck. 

Collets are made with hole sizes ranging from 
1/64 inch up, in 1/64-inch steps. The best results 
are obtained when the diameter of the work is 
exactly the same size as the dimension stamped 
on the collet. 

To ensure accuracy of the work when using 
the draw-in collet chuck, be sure that the contact 
surfaces of the collet and the closing sleeve are 
free of chips and dirt. NOTE: The standard collet 
has a round hole, but special collets for square 
and hexagonal shapes are available. 

The RUBBER COLLET CHUCK (fig. 7-28) 
is designed to hold any bar stock from 1/16 inch 
up to 1 3/8 inch. It is different from the draw-in 
type collet previously mentioned in that the bar 
stock does not have to be exact in size. 

The rubber flex collet consists of rubber and 
hardened steel plates. The nose of the chuck has 




28.305 



Figure 7-26. Three-jaw universal chuck. 



28.91X 
Figure 7-27. Draw-in collet chuck assembled. 




NOSE 

LOCKING 
RING 



7/8"- 1" COLLET 



1/16"- 1/8" COLLET 



28.306 



Figure 7-28. Rubber flex collet chuck. 



external threads, and, by rotating the handwheel 
(fig. 7-28), you compress the collet around the bar. 
This exerts equal pressure from all sides and 
enables you to align the stock very accurately. The 
locking ring, when pressed in, gives a safe lock 
that prevents the collet from coming loose when 
the machine is in operation. 

DRILL CHUCKS are used to hold center 
drills, straight shank drills, reamers, taps, and 
small rods. The drill chuck is mounted on a 
tapered shank or arbor which fits the Morse taper 
hole in either the headstock or tailstock spindle. 
Figure 7-29 shows the three-jaw type. A revolving 
sleeve operated by a key opens or closes the three 
jaws simultaneously to clamp and center the drill 
in the chuck. 

FACEPLATES are used for holding work 
that cannot be swung on centers or in a chuck 
because of its shape or dimensions. The T-slots 
and other openings on the surface of the faceplate 
provide convenient anchor points for bolts and 
clamps used to secure the work to the faceplate. 




28.92X 



Figure 7-29. Drill chuck. 



The faceplate is mounted on the nose of the 
spindle. 

The DRIVING PLATE is similar to a small 
faceplate and is used primarily for driving work 
that is held between centers. A radial slot receives 
the bent tail of a lathe dog clamped to the work 
to transmit rotary motion to the work. 



LATHE CENTERS 

The lathe centers shown in figure 7-30 provide 
a means for holding the work between points so 
it can be turned accurately on its axis. The 



60" POINTS 
TAPERED SHANK (MORSE TAPER) 



SH*NK (MORSE TAPER) 




LIVE CENTER 



DEAD CENTER 



28.93 



Figure 7-30. Lathe centers. 



7-19 



headstock spindle center is called the LIVE center 
because it revolves with the work. The tailstock 
center is called the DEAD center because it does 
not turn. Both live and dead centers have shanks 
turned to a Morse taper to fit the tapered holes 
in the spindles; both have points finished to an 
angle of 60. They differ only in that the dead 
center is hardened and tempered to resist the 
wearing effect of the work revolving on it. The 
live center revolves with the work and is usually 
left soft. The dead center and live center must 
NEVER be interchanged. A dead center requires 
a lubricant between it and the center hole to 
prevent seizing and burning of the center. NOTE: 
There is a groove around the hardened tail center 
to distinguish it from the live center. 

The centers fit snugly in the tapered holes of 
the headstock and tailstock spindles. If chips, dirt, 
or burrs prevent a perfect fit in the spindles, the 
centers will not run true. 




Figure 7-31. Pipe center. 




To remove the headstock center, insert a brass 
rod through the spindle hole and tap the center 
to jar it loose; you can then pull it out with your 
hand. To remove the tailstock center, run the 
spindle back as far as it will go by, turning the 
handwheel to the left. When the end of the 
tailstock screw bumps the back of the center, it 
will force the center out of the tapered hole. (See 
fig. 7-6.) 

For machining hollow cylinders, such as pipe, 
use a bull-nosed center called a PIPE CENTER. 
Figure 7-31 shows its construction. The taper 
shank A fits into the head and tail spindles in the 
same manner as the lathe centers. The conical disk 
B revolves freely on the collared end. Different 
size disks are supplied to accommodate various 
ranges of pipe sizes. 

Ballbearing or nonfriction centers contain 
bearings that allow the point of the center to rotate 
with the workpiece while the shank remains 
stationary in the tailstock spindle. The center hole 
does not need a lubricant when this type or center 
is used. 



LATHE DOGS 

Lathe dogs are used with a driving plate or 
faceplate to drive work being machined on centers 
whenever the frictional contact alone between the 
live center and the work is not sufficient to drive 
the work. 




LATHE 
BED 



28.95X 



Fieure 7-32. Lathe doos. 



28.96X 



TJV1 fantar root 



has a regular section (square, hexagon, octagon). 
The piece to be turned is held firmly in hole A 
by setscrew B. The bent tail C projects through 
a slot or hole in the driving plate or faceplate, so 
that when the faceplate revolves with the spindle, 
it also turns the work. The clamp dog illustrated 
at the right in figure 7-32 may be used for 
rectangular or irregularly shaped work. Such work 
is clamped between the jaws. 

CENTER REST 

The center rest, also called the steady rest, is 
used for the following purposes: 

1 . To provide an intermediate support or rest 
for long slender bars or shafts being 
machined between centers. It prevents them 
from springing due to cutting pressure or 
sagging as a result of their otherwise un- 
supported weight. 

2. To support and provide a center bearing 
for one end of work, such as a spindle, 
being bored or drilled from the end when 
it is too long to be supported by the chuck 
alone. The center rest, kept aligned by 
the ways, can be clamped at any desired 
position along the bed, as illustrated in 
figure 7-33. It is important that the jaws 
A be carefully adjusted to allow the work B 



THE WORK 



ADJUSTABLE 
JAWS 




lathe. The top half of the frame is hinged 
at C to make it easier to place the center 
rest in position without removing the work 
from the centers or changing the position 
of the jaws. 

FOLLOWER REST 

The follower rest is used to back up work of 
small diameter to keep it from springing under 
the pressure of cutting. This rest gets its name 
because it follows the cutting tool along the work. 
As shown in figure 7-34, it is attached directly to 
the saddle by bolts B. The adjustable jaws bear 
directly on the finished diameter of the work 
opposite and above the cutting tool. 

TAPER ATTACHMENT 

The taper attachment, illustrated in figure 
7-35, is used for turning and boring tapers. It is 
bolted to the back of the carriage saddle. In opera- 
tion, it is connected to the cross-slide so that it 
moves the cross-slide laterally as the carriage 
moves longitudinally, thereby causing the cutting 
tool to move at an angle to the axis of the work 
to produce a taper. 

The angle of the desired taper is set on the 
guide bar of the attachment, and the guide bar 
support is clamped to the lathe bed. 

Since the cross-slide is connected to a shoe that 
slides on the guide bar, the tool follows along a 




28.97X 



28.98X 



Figure 7-34. Follower rest. 



Figure 7-35. A taper attachment. 



7-21 





28.100X 



28.99X 



Figure 7-37. Micrometer carriage stop. 



Figure 7-36. Thread dial indicator. 




28 



Figure 7-38.-Grinder mounted on compound rest. 



line that is parallel to the guide bar and hence at 
an angle to the work axis corresponding to the 
desired taper. 

The operation and application of the taper 
attachment will be explained further under the 
subject of taper turning in chapter 10. 

THREAD DIAL INDICATOR 

The thread dial indicator, shown in figure 
7-36, lets you quickly return the carriage to the 
beginning of the thread to set up successive cuts. 
This eliminates the necessity of reversing the lathe 
and waiting for the carriage to follow the thread 
back to its beginning. The dial, which is geared 
to the lead screw, indicates when to clamp the 
half-nuts on the lead screw for the next cut. 

The threading dial consists of a worm wheel 
which is attached to the lower end of a shaft and 
meshed with the lead screw. The dial is located 
on the upper end of the shaft. As the lead screw 
revolves, the dial turns. The graduations on the 
dial indicate points at which the half-nuts may be 
engaged. When the threading dial is not being 
used, it should be disengaged from the lead screw 
to prevent unnecessary wear to the worm wheel. 

CARRIAGE STOP 

You can attach the carriage stop to the bed 
at any point where you want to stop the carriage. 
The carriage stop is used principally in turning, 
facing, or boring duplicate parts; it eliminates the 
need for repeated measurements of the same 
dimension. To operate the carriage stop, set the 
stop at the point where you want to stop the feed. 
Just before the carriage reaches this point, shut 
off the automatic feed and carefully run the 
carriage up against the stop. 

Carriage stops are provided with or without 
micrometer adjustment. Figure 7-37 shows a 
micrometer carriage stop. Clamp it on the ways 
in the approximate position required and then 
adjust it to the exact setting using the micrometer 
adjustment. NOTE: Do not confuse this stop with 
the automatic carriage stop that automatically 
stops the carriage by disengaging the feed or 
stopping the lathe. 

GRINDING ATTACHMENT 

The grinding attachment, illustrated in figure 
7-38, is a portable grinder with a base that fits 



on the compound rest in the same manner as the 
toolpost. Like the cutting tool, the grinding 
attachment can be fed to the work at any angle. 
It is used for grinding hard-faced valve disks and 
seats, for grinding lathe centers, and for all kinds 
of cylindrical grinding. For internal grinding, 
small wheels are used on special quills (extensions) 
screwed onto the grinder shaft. 



MILLING ATTACHMENT 

The milling attachment adapts the lathe to 
perform milling operations on small work, 
such as cutting key ways, slotting screwheads, 
machining flats, and milling dovetails. Figure 7-39 
illustrates the setup for milling a dovetail. 

The milling cutter is held in an arbor driven 
by the lathe spindle. The work is held in a vise 
on the milling attachment. The milling attachment 
is mounted on the cross-slide and therefore its 
movement can be controlled by the longitudinal 
feed and cross feed of the lathe. The depth of the 
cut is regulated by the longitudinal feed while the 
length of the cut is regulated by the cross feed. 
Vertical motion is controlled by the adjusting 
screw at the top of the attachment. The vise can 
be set at any angle in a horizontal or vertical plane. 




28.102X 



Figure 7-39. Milling attachment. 




28.103X 



Figure 7-40. A bench lathe. 



A milling attachment is unnecessary in shops 
equipped with milling machines. 



TRACING ATTACHMENTS 

A tracing attachment for a lathe is useful 
whenever you have to make several parts that are 
identical in design. A tracer is a hydraulically 
actuated attachment that carries the cutting tool 
on a path identical to the shape and dimensions 
of a pattern or template of the part to be made. 
The major parts of the attachment are a hydraulic 
power unit, a tracer valve to which the stylus that 
follows the template is attached, a cylinder and 
slide assembly that holds the cutting tool and 
moves in or out on the command of the tracer 
valve hydraulic pressure output, and a template 
rail assembly that holds the template of the 
part to be made. There are several different 
manufacturers of tracers, and each tracer has a 
slightly different design and varying operating 
features. Tracers can be used for turning, 
facing, and boring and are capable of main- 
taining a dimensional tolerance equal to that 
of the lathe being used. Templates for the 
tracer can be made from either flat steel or 
aluminum plate or from round bar stock. It is 




mismachined dimension will be reproduced on the 
parts to be made. 

OTHER TYPES OF LATHES 

The type of engine lathe that has been 
described in this chapter is the general-purpose, 
screw cutting precision lathe that is universally 
used in the machine shops of ships in the Navy. 
Repair ships also carry other types. A short 
description of some other types follows. 

TOOLROOM LATHE is the name com- 
monly applied to an engine lathe intended 



tools. 

A BENCH LATHE (fig. 7-40) is a small 
engine lathe mounted on a bench. Such lathes are 
sometimes used in the toolroom of repair ships. 

The GAP (EXTENSION) LATHE shown in 
figure 7-41 has a removable bed piece shown on 
the deck in front of the lathe. This piece can be 
removed from the lathe bed to create a gap into 
which work of larger diameter may be swung. 
Some gap lathes are designed so that the ways can 
be moved longitudinally to create the gap. 



7-25 



BASIC ENGINE LATHE OPERATIONS 



In chapter 7 you became familiar with the 
basic design and functions of the engine lathe and 
the basic attachments used with the engine lathe. 
In this chapter, we will discuss the fundamentals 
of engine lathe operations. 



PREOPERATIONAL PROCEDURES 

As a Machinery Repairman you will be 
required to know and use specific procedures that 
you must follow both prior to and during opera- 
tion of the engine lathe. First, you must be fully 
aware of and comply with all machine operator 
safety precautions. Second, you must be familiar 
with the specific type of engine lathe you are going 
to operate. 



LATHE SAFETY PRECAUTIONS 

In machine operations, there is one sequence 
of events that you must always follow. SAFETY 
FIRST, ACCURACY SECOND, AND SPEED 

LAST. With this in mind, we will discuss the 
safety of lathe operations first. 

1 . Prepare yourself by rolling up your shirt 
sleeves and removing your watch, rings, 
and other jewelry that might become 
caught while you operate a machine. 

2. Wear safety glasses or an approved face 
shield at all times when you operate a lathe 
or when you are in the area of lathes that 
are in operation. 

3. Be sure the work area is clear of obstruc- 
tions that might cause you to trip or fall. 

4. Keep the deck area around your machine 
clear of oil or grease to prevent the 
possibility of anyone slipping and falling 
into the machine. 



5. Always get someone to help you handle 
heavy or awkward parts, stock, or 
machine accessories. 

6. Never remove chips with your bare hands; 
use a stick or brush. (Stop the machine 
while you remove the chips.) 

7. Prevent long chips from being caught in 
the chuck by using good chip control 
procedures on your setup. 

8. Disengage the machine feed before you 
talk to anyone. 

9. Know how to stop the machine quickly 
if an emergency arises. 

10. Be attentive, not only to the operation of 
your machine, but the events going on 
around it. 

1 1 . If you must operate a lathe while under- 
way, be especially safety conscious. 
(Machines should be operated only in 
relatively calm seas.) 

12. Know where the cutting tool is while you 
take measurements or make adjustments 
to the machine. 

13. Always observe the specific safety 
precautions posted for the machine you 
are operating. 



MACHINE CHECKOUT 

Before you attempt to operate any lathe, make 
sure you know how to run it. Read all operating 
instructions supplied with the machine. Know 
where the various controls are and how to operate 
them. When you are satisfied that you know how 
the controls work, check to see that the spindle 
clutch and the power feeds are disengaged; then 



8-1 



phases of operation, as follows: 

1. Shift the speed change levers into the 
various combinations; start and stop the spindle 
after each change. Get the feel of this operation. 

2. With the spindle running at its slowest 
speed, try out the operation of the power feeds 
and observe their action. Take care not to run the 
carriage too near the limits of its travel. Learn 
how to reverse the direction of feeds and how to 
disengage them quickly. Before engaging either 
of the power feeds, operate the hand controls 
to be sure the parts involved are free for 
running. 

3. Try out the operation of engaging the 
lead screw for thread cutting. Remember 
that you must disengage the feed mechanism 
before you can close the half-nuts on the lead 
screw. 

4. Practice making changes with the QUICK 
CHANGE GEAR MECHANISM by referring 
to the thread and feed index plate on the 
lathe you intend to operate. Remember that 
you may make changes in the gear box 
with the lathe running slowly, but you must 
stop the lathe to make speed changes by 
shifting gears in the main gear train. 

Maintenance is an important operational 
procedure for lathes and must be performed 
according to the Navy's Planned Maintenance 
System (PMS). This subject is covered in detail 
in the Military Requirements for Petty Officers 
training manual. In addition to the regular 
planned maintenance, make it a point to oil 
your lathe daily wherever oil holes are provided. 
Oil the ways often, not only to lubricate 
them but to protect their scraped surfaces. 
Oil the lead screw often while it is in use 
to preserve its accuracy. A worn lead screw 
lacks precision in thread cutting. Be sure 
the headstock is filled up to the oil level; 
drain out and replace the oil when it becomes 
dirty or gummy. If your lathe is equipped 
with an automatic oiling system for some parts, 
be sure all those parts are getting oil. Make it a 
habit to CHECK frequently for lubrication of all 
moving parts. 

Do not treat your machine roughly. When you 
shift gears to change speed or feed, remember that 



into engagement. Disengage the clutch and stop 
the lathe before shifting gears. 

Before engaging the longitudinal feed, be 
certain that the carriage clamp screw is loose and 
that the carriage can be moved by hand. Avoid 
running the carriage against the headstock or 
tailstock while the machine is under power feed; 
carriage pressure against the headstock or the 
tailstock puts an unnecessary strain on the lathe 
and may jam the gears. 

Do not neglect the motor just because it may 
be out of sight; check its lubrication. If it does 
not run properly, notify the Electrician's Mate 
whose duty it is to care for motors. He or she will 
cooperate with you to keep it in good condition. 
In a machine that has a belt drive from the motor 
to the lathe, avoid getting oil or grease on the belt 
when you oil the lathe or the motor. 

Keep your lathe CLEAN. A clean and orderly 
machine is an indication of a good mechanic. Dirt 
and chips on the ways, the lead screw, or the cross 
feed screws will cause serious wear and impair the 
accuracy of the machine. 

Never put wrenches, files, or other tools on 
the ways. If you must keep tools on the bed, use 
a board to protect the finished surfaces of the 
ways. 

Never use the bed or carriage as an anvil; 
remember that the lathe is a precision machine 
and nothing must be allowed to destroy its 
accuracy. 



SETTING UP THE LATHE 

Before starting a lathe machining operation, 
always ensure that the machine is set up for the 
job you are doing. If the work is mounted between 
centers, check the alignment of the dead center 
with the live center and make any required 
changes. Ensure that the toolholder and the 
cutting tool are set at the proper height and angle. 
Check the workholding accessory to ensure that 
the workpiece is held securely. Use the center rest 
or follower rest to support long workpieces. 



PREPARING THE CENTERS 

The first step in preparing the centers is to see 
that they are accurately mounted in the headstock 



8-2 



will impair accuracy by preventing a perfect fit 
of the bearing surfaces. Be sure that there are no 
burrs in the spindle hole. If you find burrs, 
remove them by carefully scraping or reaming 
the surface with a Morse taper reamer. Burrs 
will produce the same inaccuracies as chips and 
dirt. 

Center points must be accurately finished to 
an included angle of 60. Figure 8-1 shows the 
method of checking the angle with a center gauge. 
The large notch of the center gauge is intended 
for this particular purpose. If the test shows that 
the point is not perfect, true the point in the lathe 
by taking a cut over the point with the compound 
rest set at 30. To true a hardened tail center, 
either anneal it and then machine it or grind it 
if a grinding attachment is available. 

Aligning and Testing 

To turn a shaft straight and true between 
centers, be sure the centers are in the same plane 
parallel to t!ie ways of the lathe. You can align 
the centers by releasing the tailstock from the ways 
and then moving the tailstock laterally with two 
adjusting screws. At the rear of the tailstock are 
two zero lines, and the centers are approximately 
aligned when these lines coincide. To check the 
approximate alignment, move the tailstock up 
until the centers almost touch and observe their 
relative positions as shown in figure 8-2. To 




28.106X 



Figure 8-2. Aligning lathe centers. 



produce very accurate work, especially if it is long, 
use the following procedure to determine and 
correct errors in alignment not otherwise detected. 
Mount the work to be turned, or a piece of 
stock of similar length, on the centers. With a 
turning tool in the toolpost, take a small cut to 
a depth of a few thousandths of an inch at the 
headstock end of the work. Then remove the work 
from the centers to allow the carriage to be run 
back to the tailstock without withdrawing the tool. 
Do not touch the tool setting. Replace the work 
in the centers, and with the tool set at the previous 
depth take another cut coming in from the 
tailstock end. Compare the diameters of these cuts 
with a micrometer. If the diameters are exactly 
the same, the centers are in perfect alignment. If 
they are different, adjust the tailstock in the direc- 
tion required by using the set-over adjusting 
screws. Repeat the above test and adjustment until 
a cut at each end produces equal diameters. 




28.105 



Figure 8-1. Checking center point with a center gauge. 



8-3 



You can also check for positive alignment of 
the centers by placing a test bar between the 
centers and checking both ends of the bar with 
a dial indicator clamped in the toolpost (fig. 8-3). 
If the reading on the dial is zero at both ends of 
the bar, the centers are aligned. The tailstock must 
be clamped to the ways and the test bar must be 
properly adjusted between centers so there is no 
end play when you take the indicator readings. 

Another method you can use to check for 
positive alignment of lathe centers is to take a light 
cut over the work held between centers. Then 
measure the work at each end with a micrometer. 
If the readings differ, adjust the tailstock to 
remove the difference. Repeat the procedure until 
the centers are aligned. 

Truing and Grinding 

To machine or true a lathe center, remove the 
faceplate from the spindle. Then insert the live 
center into the spindle and set the compound rest 
at an angle of 30 with the axis of the spindle, 
as shown in figure 8-4. Place a round-nose tool 
in the toolpost and set the cutting edge of the tool 
at the exact center point of the lathe center. 
Machine a light cut on the center point and test 
the point with a center gauge. All lathe centers, 
regardless of their size, are finished to an included 
angle of 60. 

Recall that if you must true the tailstock 
spindle lathe center, anneal it and machine it in 
the headstock spindle, following the same opera- 
tions described for truing a live center; then 
remove, harden, and temper the spindle. It is now 
ready for use in the tailstock. 

Also if a toolpost grinder is available, you may 
true the hardened center by grinding it without 
annealing it. As in machining, the first step after 
placing the center in the headstock spindle is to 




28.108X 



Figure 8-4. Machining a lathe center. 



set the compound rest over to 30 with the axis 
of the lathe. Second, mount a toolpost grinder 
or grinding attachment on the lathe as shown in 
figure 8-5. Third, cover the exposed ways of the 
lathe with cloth or paper to keep the grinding grit 
out of the bearing surfaces of the bed and cross- 
slides. Fourth, put the headstock in gear to give 
approximately 200 rpm to the spindle and take 
a light cut over the center point, feeding the wheel 
across the point with the compound rest feed 
handle. Continue to feed the wheel back and forth 
until it is cutting evenly all around the entire length 
of the center point. Then check the angle with a 
center gauge. Reset the compound rest if necessary 
and continue grinding until the center fits the 
center gauge exactly. To check the accuracy of 
the fit, place a light beneath the center and look 
for light between the center point surface and the 
edge of the center point gauge. 



HEADSTOCK CENTER 



TEST BAR 


TAIL 


STOCK 


CENTER 


__ 


; ; ; -? 




s 


' i i, i 'V i , ' 1 1 , ' 




K 











!'>!k^ 



DIAL INDICATOR 



28.107 



LATHE 
CENTER 




GRINDING 
WHEEL 



LATHE 

SPINDLE 

AXIS 



TOOLPOST. 
GRINDER 



Figure 8-5. Grinding a lathe center. 



Additional information on the operation of 
the toolpost grinder is provided later in this 
chapter. 

SETTING THE TOOLHOLDER 
AND CUTTING TOOL 

The first requirement for setting the tool is to 
have it rigidly mounted on the tool post holder. 
Be sure the tool sits squarely in the toolpost and 
that the setscrew is tight. Reduce overhang 
as much as possible to prevent the tool from 
springing during cutting. If the tool has too much 
spring the point of the tool will catch in the work, 
causing chatter and damaging both the tool and 
the work. The relative distances of A and B in 
figure 8-6 show the correct overhang for the tool 




28.110X 



Figure 8-6. Tool overhang. 



UIC W1UU1 \JL LUC CUlllil 

the shank when you use a carbide insert type 
cutting tool. 

The point of the tool must be correctly 
positioned on the work. When you are using a 
high-speed cutting tool to straight turn steel, cast 
iron, and other relatively hard metals, set the point 
on center. The point of a high-speed steel cutting 
tool being used to cut aluminum, copper, brass, 
and other soft metals should be set exactly on 
center. The point of cast alloy (stellite and so 
on), carbide, and ceramic cutting tools should be 
placed exactly on center regardless of the material 
being cut. The tool point should be placed on 
center for threading, turning tapers, parting 
(cutting-off) or boring. 

You can adjust the height of the tool in the 
toolholder illustrated in figure 8-6 by moving the 
half-moon wedge beneath the toolholder in or out 
as required. The quick-change type toolholder 
usually has an adjusting screw to stop the tool at 
the correct height. Some square turret type 
toolholders require a shim beneath the tool to 
adjust the height. 

There are several methods you can use to set 
a tool on center. You can place a dead center in 
the tailstock and align the point of the tool with 
the point of the center. The tailstock spindle on 
many lathes has a line on the side that represents 
the center. You can also place a 6-inch rule against 
the workpiece in a vertical position and move the 
cross-slide in until the tool lightly touches the rule 
and holds it in place. Look at the rule from 
the side to determine if the height of the 
tool is correct. The rule will be straight up 
and down when the tool is exactly on center and 
will be at an angle when the tool is either high 
or low. 



METHODS OF HOLDING 
THE WORK 

You cannot perform accurate work if the work 
is improperly mounted. Requirements for proper 
mounting are: 

1. The work centerline must be accurately 
centered along the axis of the lathe spindle. 



8-5 



2. The work must be held rigidly while being 
turned. 

3. The work must not be sprung out of shape 
by the holding device. 

4. The work must be adequately supported 
against any sagging caused by its own weight and 
against springing caused by the action of the 
cutting tool. 

There are four general methods of holding 
work in the lathe: (1) between centers, (2) on a 
mandrel, (3) in a chuck, and (4) on a faceplate. 
Work may also be clamped to the carriage for 
boring and milling; the boring bar or milling cutter 
is held and driven by the headstock spindle. 

Other methods of holding work to suit special 
conditions are: (1) one end on the live center or 
in a chuck with the other end supported in a center 
rest, and (2) one end in a chuck with the other 
end on the dead center. 

HOLDING WORK BETWEEN CENTERS 

To machine a workpiece between centers, drill 
center holes in each end to receive the lathe 
centers. Secure a lathe dog to the workpiece and 
then mount the work between the live and dead 
centers of the lathe. 

Centering the Work 

To center drill round stock such as drill-rod 
or cold-rolled steel, secure the work to the head 
spindle in a universal chuck or a draw-in collet 
chuck. If the work is too long and too large to 
be passed through the spindle, use a center rest 
to support one end. It is good shop practice to 
first take a light finishing cut across the face of 
the end of the stock to be center drilled. This will 
provide a smooth and even surface and will help 
prevent the center drill from "wandering" or 
breaking. The centering tool is held in a drill chuck 
in the tailstock spindle and fed to the work by the 
tailstock hand wheel (fig. 8-7). 

If you must center a piece very accurately, 
bore the tapered center hole after you center drill 



CENTERING 
TOOL 



to correct any run-out of the drill. You can do 
this by grinding a tool bit to fit a center gauge 
at a 60 angle. Then, with the toolholder held in 
the toolpost, set the compound rest at 30 with 
the line of center as shown in figure 8-8. Set the 
tool exactly on the center for height and adjust 
the tool to the proper angle with the center gauge 
as shown at A. Feed the tool as shown at B to 
correct any run-out of the center. The tool bit 
should be relieved under the cutting edge as shown 
at C to prevent the tool from dragging or rubbing 
in the hole. 

For center drilling a workpiece, the combined 
drill and countersink is the most practical tool. 
Combined drills and countersinks vary in size and 
the drill points also vary. Sometimes a drill point 
on one end will be 1/8 inch in diameter and the 
drill point on the opposite end will be 3/16 inch 
in diameter. The angle of the center drill is always 
60 so that the countersunk hole will fit the angle 
of the lathe center point. 

If a center drill is not available, you may center 
the work with a small twist drill. Let the drill enter 
the work a sufficient depth on each end; then 
follow with a countersink which has a 60 point. 

The drawing and tabulation in figure 8-9 show 
the correct size of the countersunk center hole for 
the diameter of the work. 

In center drilling, use a drop or two of oil on 
the drill. Feed the drill slowly and carefully to 
prevent breaking the tip. Use extreme care when 
the work is heavy, because it is then more difficult 
to "feel" the proper feed of the work on the 
center drill. 

If the center drill breaks in countersinking and 
part of the broken drill remains in the work, you 
must remove the broken part. Sometimes you can 
jar it loose, or you may have to drive it out by 
using a chisel. But it may stick so hard that you 



-E3 






Figure 8-7. Drilling center hole. 



Figure 8-8. Boring center hole. 



w 





COMBINED DRILL & COUNTERSINK 




NO.OFCOMB.DRILL 
AND COUNTERSINK 


DIA.OF WORK 
(W) 


LARGE DIAMETER OF 
COUNTERSUNK HOLE(C; 


DIA.OF DRILL 
(D) 


DIA. OF BODY 
(F) 


1 


3/i6"T05/l6" 


1/8" 


1/16" 


13/64" 


2 


3/8" TO l" 


1/16" 


3/32" 


3/16" 


3 


1 1/4" TO 2" 


1/4" 


1/8" 


5/16" 


4 


2 1/4" TO 4" 


5/16" 


5/32" 


7/16" 



28.113X 



Figure 8-9. Correct size of center holes. 



cannot easily remove it. If so, anneal the broken 
part of the drill and drill it out. 

The importance of having proper center holes 
in the work and a correct angle on the point of 
the lathe centers cannot be overemphasized. To 
do an accurate job between centers on the lathe, 
you must countersink holes of the proper size and 
depth, and be sure the points of the lathe centers 
are true and accurate. 

Figure 8-10 shows correct and incorrect 
countersinking for work to be machined on 
centers. In example A, the correctly countersunk 
hole is deep enough so that the point of the lathe 
centers does not come in contact with the bottom 
of the hole. 

In example B of figure 8-10, the countersunk 
hole is too deep, causing only the outer edge of 




CORRECT 




the hole to rest on the lathe center. Work cannot 
be machined on centers countersunk in this 
manner. 

Example C shows a piece of work that has 
been countersunk with a tool having too large an 
angle. This work rests on the point of the lathe 
center only. It is evident that this work will soon 
destroy the end of the lathe center, thus making 
it impossible to do an accurate job. 

Mounting the Work 

Figure 8-11 shows correct and incorrect 
methods of mounting work between centers. In 




Tl 



CORRECT 




INCORRECT 



28.114X 28.115X 

Figure 8-10. Examples of center holes. Figure 8-11. Examples of work mounted between centers. 



to the work and rigidly held by the setscrew. The 
tail of the dog rests in the slot of the drive plate 
and extends beyond the base of the slot so that 
the work rests firmly on both the headstock center 
and tailstock center. 

In the incorrect example, the tail of the dog 
rests on the bottom of the slot on the faceplate 
at A, thereby pulling the work away from the 
center points, as shown at B and C, causing the 
work to revolve eccentrically. 

When you mount work between centers for 
machining, there should be no end play between 
the work and the dead center. However, if the 
work is held too tightly by the tail center, when 
the work begins revolving it will heat the center 
point and destroy both the center and the work. 
To prevent overheating, lubricate the tail center 
with a heavy oil or a lubricant specially made for 
this purpose. 



HOLDING WORK ON A MANDREL 

Many parts, such as bushings, gears, collars, 
and pulleys, require all the finished external 
surfaces to run true with the hole which extends 
through them. That is, the outside diameter must 
be true with the inside diameter or bore. 

General practice is to finish the hole to a 
standard size, within the limit of the accuracy 
desired. Thus, a 3/4-inch standard hole will have 
a finished dimension of from 0.7505 to 0.7495 
inch, or a tolerance of one-half of one thousandth 
of an inch above or below the true standard size 
of exactly 0.750 inch. First, drill or bore the hole 
to within a few thousandths of an inch of the 
finished size; then remove the remainder of the 
material with a machine reamer. 

Press the piece on a mandrel tightly enough 
so the work will not slip while it is machined and 
clamp a dog on the mandrel, which is mounted 
between centers. Since the mandrel surface runs 
true with respect to the lathe axis, the turned 
surfaces of the work on the mandrel will be true 
with respect to the hole in the piece. 

A mandrel is simply a round piece of steel of 
convenient length which has been centered 
and turned true with the centers. Commercial 
mandrels are made of tool steel, hardened and 
ground with a slight taper (usually 0.0005 inch per 
inch). On sizes up to 1 inch the small end is usually 
one-half of one thousandth of an inch under the 
standard size of the mandrel, while on larger sizes 



an inch under standard. This taper allows th 
standard hole in the work to vary according tc 
the usual shop practice, and still provides the 
necessary fit to drive the work when the mandre 
is pressed into the hole. However, the taper is noi 
great enough to distort the hole in the work. Th( 
countersunk centers of the mandrel are lapped foi 
accuracy, while the ends are turned smaller thar 
the body of the mandrel and are provided witl 
flats, which give a driving surface for the lath< 
dog. 

The size of the mandrel is always marked 01 
the large end to avoid error and for convenient 
in placing work on it. The work is driven O] 
pressed on from the small end and removed th< 
same way. 

When the hole in the work is not standard size 
or if no standard mandrel is available, make a sof 
mandrel to fit the particular piece to be machined 

Use a few drops of oil to lubricate the surface 
of the mandrel before pressing it into the work 
because clean metallic surfaces gall or stick whei 
pressed together. If you do not use lubricant, yoi 
will not be able to drive the mandrel out withou 
ruining the work. 

Whenever you machine work on a mandrel 
be sure that the lathe centers are true an< 
accurately aligned; otherwise, the finished turne< 
surface will not be true. Before turning accurat 
work, test the mandrel on centers before placinj 
any work on it. The best test for run-out is on 
made with a dial indicator. Mount the indicate 
on the toolpost so the point of the indicator jus 
touches the mandrel. As the mandrel is turnei 
slowly between centers, any run-out will b 
registered on the indicator dial. 

If run-out is indicated and you cannot correc 
it by adjusting the tailstock, the mandrel itself i 
at fault (assuming that the lathe centers are true 
and cannot be used. The countersunk holes ma 
have been damaged, or the mandrel may hav 
been bent by careless handling. Be sure you alway 
protect the ends of the mandrel when you pres 
or drive it into the work. A piece of work mounte 
on a mandrel must have a tighter press fit to th 
mandrel for roughing cuts than for finishing cuts 
Thick-walled work can be left on the mandrel fo 
the finishing cut but thin-walled work should b 
removed from the mandrel after the roughing ci 



8-8 



and lightly reloaded on the mandrel before the 
finish cut is taken. 

In addition to the standard lathe mandrel just 
described, there are expansion mandrels, gang 
mandrels, and eccentric mandrels. 

An EXPANSION mandrel is used to hold 
work that is reamed or bored to nonstandard 
size. Figure 8-12 shows an expansion mandrel 
composed of two parts: a tapered pin that has a 
taper of approximately 1/16 inch for each inch' 
of length and an outer split shell that is tapered 
to fit the pin. The split shell is placed in the work 
and the tapered pin is forced into the shell, caus- 
ing it to expand until it holds the work properly. 

A GANG mandrel (fig. 8-13) is used for 
holding several duplicate pieces such as gear 



WORK 




MANDREL 



Figure 8-13. Gang mandrel. 



blanks. The pieces are held tightly against a 
shoulder by a nut at the tailstock end. 

An ECCENTRIC mandrel has two sets of 
countersunk holes, one pair of which is off-center 




28.116 



Fionrp 8.12.. A snlit-sh<>ll pvnnnsinn mandrel. 



an amount equal to the eccentricity of the work 
to be machined. Figure 8-14 illustrates its applica- 
tion: A is to be machined concentric with the hole 
in the work, while B is to be machined eccentric 
to it. 

HOLDING WORK IN CHUCKS 

The independent chuck and universal chuck 
are used more often than other workholding 
devices in lathe operations. A universal chuck is 
used for holding relatively true cylindrical work 
when accurate concentricity of the machined 
surface and holding power of the chuck are 
secondary to the time required to do the job. An 
independent chuck is used when the work is 
irregular in shape, must be accurately centered, 
or must be held securely for heavy feeds and depth 
of cut. 

Four-Jaw Independent Chuck 

Figure 8-15 shows a rough casting mounted 
in a four- jaw independent lathe chuck on the 
spindle of the lathe. Before truing the work, 
determine which part you wish to turn true. To 
mount a rough casting in the chuck, proceed as 
follows: 

1. Adjust the chuck jaws to receive the 
casting. Each jaw should be concentric with the 
ring marks indicated on the face of the chuck. If 
there are no ring marks, set the jaws equally 
distant from the circumference of the chuck body. 

2. Fasten the work in the chuck by turning 
the adjusting screw on jaw No. 1 and jaw No. 3, 
a pair of jaws which are opposite each other. Next 
tighten jaws No. 2 and No. 4 (opposite each 
other). 

3. At this stage the work should be held in 
the jaws just tightly enough so it will not fall out 
of the chuck while being trued. 





Figure 8-14. Work on an eccentric mandrel. 



COMPOUND REST 



Figure 8-15. Work mounted in a 4-jaw independent chuck. 



4. Revolve the spindle slowly, and with a piece 
of chalk mark the high spot (A in fig. 8-15) on 
the work while it is revolving. Steady your hand 
on the toolpost while holding the chalk. 

5. Stop the spindle. Locate the high spot on 
the work and adjust the jaws in the proper 
direction to true the work by releasing the jaw 
opposite the chalk mark and tightening the one 
nearest the tank. 

6. Sometimes the high spot on the work will 
be located between adjacent jaws. When it is, 
loosen the two opposite jaws and tighten the jaws 
adjacent to the high spot. 

7. When the work is running true in the 
chuck, tighten the jaws gradually, working the 
jaws in pairs as described previously, until all four 
jaws clamp the work tightly. Be sure that the back 
of the work rests flat against the inside face of 
the chuck, or against the faces of the jaw stops 
(B in figure 8-15). 

Use the same procedure to clamp semi-finished 
or finished pieces in the chuck, except center these 
pieces more accurately in the chuck. If the run- 
out tolerance is very small, use a dial indicator 
to determine the run-out. 

Figure 8-16 illustrates the use of a dial test 
indicator in centering work that has a hole bored 
in its center. As the work is revolved, the high spot 
is indicated on the dial of the instrument to a 
thousandth of an inch. The jaws of the chuck are 
adjusted on the work until the indicator hand 
registers no deviation as the work is revolved. 

When the work consists of a number of 
duplicate parts that are to be tightened in the 





28.120X 
Figure 8-16. Centering work with a dial indicator. 



chuck, release two adjacent jaws and remove the 
work. Place another piece in the chuck and 
retighten the two jaws just released. 

Each jaw of a lathe chuck, whether an 
independent or a universal chuck, has a number 
stamped on it to correspond to a similar number 
on the chuck. When you remove a chuck jaw for 
any reason, always put it back into the proper slot. 

When the work to be chucked is frail or light, 
tighten the jaw carefully so the work will not 
bend, break, or spring. 

To mount rings or cylindrical disks on a 
chuck, expand the chuck jaws against the inside 
of the workpiece. (See fig. 8-17.) 

Regardless of how you mount the workpiece, 
NEVER leave the chuck wrench in the chuck while 
the chuck is on the lathe spindle. If the lathe 
should be started, the wrench could fly off the 
chuck and injure you or a bystander. 



Three-Jaw Universal Chuck 

A three-jaw universal, or scroll, chuck allows 
all jaws to move together or apart in unison. A 
universal chuck will center almost exactly at the 
first clamping, but after a period of use it may 
develop inaccuracies of from .002 to .010 inch in 
centering the work, requiring the run-out of the 
work to be corrected. Sometimes you can make 
the correction by inserting a piece of paper or thin 
shim stock between the jaw and the work on the 
HIGH SIDE. 



28.121 

Figure 8-17. Work held from inside by a 4-jaw independent 
chuck. 



When you chuck thin sections, be careful not 
to clamp the work too tightly, since the diameter 
of the piece will be machined while the piece is 
distorted. Then, when you release the pressure of 
the jaws after finishing the cut, there will be as 
many high spots as there are jaws, and the turned 
surface will not be true. 



Draw-In Collet Chuck 

A draw-in collet chuck is used for very fine 
accurate work of small diameter. Long work can 
be passed through the hollow drawbar, and short 
work can be placed directly into the collet from 
the front. Tighten the collet on the work by 
rotating the drawbar handwheel to the right. 
This draws the collet into the tapered closing 
sleeve. Turn the handle to the left to release the 
collet. 

You will get the most accurate results when 
the diameter of the work is the same as the 
dimension stamped on the collet. The actual 
diameter of the work may vary from the collet 
dimension by 0.001 inch. However, if the work 
diameter varies more than this, the accuracy of 
the finished work will be affected. Most draw-in 
collet chuck sets are sized in 1/64-inch increments 
to allow you to select a collet within the required 
tolerances. 



8-11 



Rubber Flex Collet Chuck 

A rubber flex collet chuck is basically the same 
as the draw-in type collet, except that the size 
of the stock held is not as critical. The rubber 
collets are graduated in 1/1 6-inch steps and will 
tighten down with accuracy on any size within the 
1/16-inch range. 

CARE OF CHUCKS 

To preserve a chuck's accuracy, handle it 
carefully and keep it clean. Never force a chuck 
jaw by using a pipe as an extension on the chuck 
wrench. 

Before mounting a chuck, remove the live 
center and fill the hole with a rag to prevent chips 
and dirt from getting into the tapered hole of the 
spindle. 

Clean and oil the threads of the chuck and the 
spindle nose. Dirt or chips on the threads will 
not allow the chuck to seat properly against the 
spindle shoulder and will prevent the chuck from 
running true. Screw the collar carefully onto the 
chuck and tighten it enough to make it difficult 
to remove the chuck. Never use mechanical power 
to install a chuck, but rotate the collar with your 
left hand while you support the chuck in the 
hollow of your right arm. 

To remove a chuck, place a chuck wrench in 
the square hole in one of the jaws and strike a 
smart blow on the wrench handle with your hand 
in the direction you wish the chuck to rotate. 
When you mount or remove a heavy chuck, lay 
a board across the bed ways to protect them and 
to help support the chuck as you put it on or take 
it off. Most larger chucks are drilled and tapped 
to accept a padeye for lifting with a chainfall. 



The procedures for mounting and removing 
faceplates are the same as for mounting and 
removing chucks. 

Figure 8-18 shows a simple device made of 
brass wire for cleaning the threads of a chuck or 
faceplate. 

HOLDING WORK ON A FACEPLATE 

A faceplate used for mounting work that can- 
not be chucked or turned between centers because 
of its peculiar shape. A faceplate is also used when 
holes are to be accurately machined in flat work, 
as in figure 8-19, or when large and irregularly 
shaped work is to be faced on the lathe. 

Work is secured to the faceplate by bolts, 
clamps, or any suitable clamping means. The 
holes and slots in the faceplate are used to anchor 
the holding bolts. Angle plates may be used to 
locate the work at the desired angle, as shown in 
figure 8-20. (Note the counterweight added for 
balance.) 

For work to be mounted accurately on a 
faceplate, the surface of the work in contact 
with the faceplate must be accurate. Check the 
accuracy with a dial indicator. If you find run- 
out, reface the surface of the work that is in 
contact with the faceplate. It is good practice to 
place a piece of paper between the work and the 
faceplate to keep the work from slipping. 

Before securely clamping the work, move it 
about on the surface of the faceplate until the 
point to be machined is centered accurately over 
the axis of the lathe. Suppose you wish to bore 
a hole, the center of which has been laid out and 
marked with a prick punch. First, clamp the work 
to the approximate position on the faceplate. 
Then slide the tailstock up to where the dead 



n 





28.122X 

Figure 8-18. Tool for cleaning thread of a chuck or 
faceplate. 



28.123X 

Figure 8-19. Eccentric machining of work mounted on a 
faceplate. 



8-12 



center just touches the work. Note, the dead 
center should have a sharp, true point. Now 
revolve the work slowly and, if the work is off 
center, the point of the dead center will scribe a 
circle on the work. If the work is on center, the 
point of the dead center will coincide with the 
prick punch mark. 

HOLDING WORK ON THE CARRIAGE 

If a piece of work is too large or bulky to 
swing conveniently in a chuck or on a faceplate, 
you can bolt it to the carriage or the cross-slide 
and machine it with a cutter mounted on the 
spindle. Figure 8-21 shows a piece of work being 
machined by a fly cutter mounted in a boring bar 
which is held between centers and driven by a lathe 
dog. 

USING THE CENTER REST 
AND FOLLOWER REST 

Long slender work often requires support 
between its ends while it is turned; otherwise 
the work would spring away from the tool and 
chatter. The center rest is used to support such 
work so it can be turned accurately at a faster feed 





28.128X 
Figure 8-21. Work mounted on a carriage for boring. 



and cutting speed than would be possible without 
the center rest. (See fig. 8-22). 

Place the center rest where it will give the 
greatest support to the piece to be turned. This 
is usually at about the middle of its length. 

Ensure that the center point between the jaws 
of the center rest coincides exactly with the axis 
of the lathe spindle. To do this, place a short piece 
of stock in a chuck and machine it to the diameter 
of the workpiece to be supported. Without 
removing the stock from the chuck, clamp the 
center rest on the ways of the lathe and adjust the 




28.124X 
Figure 8-20. Work clamped to an angle plate. 



28.125X 

Figure 8-22. Use of a center rest to support work between 
centers. 



8-13 



jaws to the machined surface. Without changing 
the jaw settings, slide the center rest into position 
to support the workpiece. Remove the stock used 
for setting the center rest and set the workpiece 
in place. Use a dial indicator to true the workpiece 
at the chuck. Figure 8-23 shows how a chuck and 
center rest are used to machine the end of a 
workpiece. 

The follower rest differs from the center rest 
in that it moves with the carriage and provides 
support against the forces of the cut. To use the 
tool turn a "spot" to the desired finish diameter 
and about 5/8 to 3/4 inch wide on the workpiece. 
Then, adjust the jaws of the follower rest against 
the area you just machined. The follower rest will 
move with the cutting tool and support the point 
being machined. 

The follower rest (fig. 8-24) is indispensable 
for chasing threads on long screws, as it allows 
the cutting of a screw with a uniform pitch 
diameter. Without the follower rest, the screw 
would be inaccurate because it would spring away 
from the tool. 

Use a sufficient amount of grease, oil or other 
available lubricant on the jaws of the center rest 
and follower rest to prevent "seizing" and scoring 
the workpiece. Check the jaws frequently to see 
that they do not become hot. The jaws may 
expand slightly if they get hot and push the work 
out of alignment (when the follower rest is used) 
or binding (when the center rest is used). 



MACHINING OPERATIONS 

Up to this point, you have studied the 
preliminary steps leading up to performing 
machine work on the lathe. You have learned how 
to mount the work and the tool, and which tools 
are used for various purposes. The next step is 




to learn how to use the lathe to turn, bore, and 
face the work to the desired form or shape. 

TURNING is the machining of the outside 
surface of a cylinder. 

BORING is the machining of the inside 
surface of a cylinder. 

FACING is the machining of flat surfaces. 

Remember that accuracy is the prime requisite 
of a good machine job; so before you start, be 
sure that the centers are true and properly aligned, 
that the work is mounted properly, and that the 
cutting tools are correctly ground and sharpened. 

PLANNING THE JOB 

It is important for you to study the blueprint 
of the part to be manufactured before you begin 
machining. Check over the dimensions and note 
the points or surfaces from which they are laid 
out. Plan the steps of your work in advance to 
determine the best way to proceed. Check the 
overall dimensions and be sure the stock you 
intend to use is large enough for the job. For 
example, small design features, such as collars on 
pump shafts or valve stems, will require that you 
use stock of much larger diameter than that 
required for the main features of the workpiece. 

CUTTING SPEEDS AND FEEDS 

Cutting speed is the rate at which the surface 
of the work passes the point of the cutting tool. 
It is expressed in feet per minute (fpm). 

To find the cutting speed, multiply the 
diameter of the work (DIA) in inches times 3.1416 




28.126X 
Figure 8-23. Work mounted in a chuck and center rest. 



28.127X 

Figure 8-24. Follower rest supporting screw while thread 
is being cut. 



_ DIAX3.1416 xrpm 



The result is the peripheral or cutting speed 
in feet per minute. For example, a 2-inch diameter 
part turning at 100 rpm will produce a cutting 
speed of 



TYPE OF MATERIAL 



Cutting 
Speed (fpm) 



2 x 3. 1416 x IQO 
12 



= 52.36 fpm 



If you have selected a recommended cutting 
speed from a chart for a specific type of metal, 
you will need to figure what rpm is required to 
obtain the recommended cutting speed. Use the 
following formula: 

CS x 12 
rpm DIAxS.1416 

Table 8-1 gives the recommended approximate 
cutting speeds for various metals, using a high- 
speed steel tool bit. To obtain an approximate 
cutting speed for the other types of cutting 
tool materials multiply the cutting speeds 
recommended in table 8-1 and other charts, which 
you will find in different handbooks, by the 
following factors: 



Carbon steel tools 



50% of HSS, multiply by 
0.5 



Cast alloy tools 160% of HSS, multiply 
by 1.6 



Carbide tools 



Ceramic tools 



200% to 400% of HSS, 
multiply by 2.0 to 4.0 

400% to 1600% of HSS, 
multiply by 4.0 to 16.0 



FEED is the amount the tool advances in each 
revolution of the work. It is usually expressed in 
thousandths of an inch per revolution of the 
spindle. The index plate on the quick-change gear 
box indicates the setup for obtaining the feed 
desired. The amount of feed to use is best 
determined from experience. 

Cutting speeds and tool feeds are determined 
by various considerations: the hardness and 
toughness of the metal being cut; the quality, 
shape, and sharpness of the cutting tool; the depth 



Low carbon steel 
Medium carbon steel 
High carbon steel 
Stainless steel, Cl 302, 304 
Stainless steel, Cl 310,316 
Stainless steel, Cl 410 
Stainless steel, Cl 416 
Stainless steel, Cl 17-4, pH 
Alloy steel, SAE 4 130, 4140 
Alloy steel, SAE 4030 
Gray cast iron 
Aluminum alloys 
Brass 
Bronze 

Nickel alloy, Monel 400 
Nickel alloy, Monel K500 
Nickel alloy, Inconel 
Titanium alloy 



40-140 

70-120 

65-100 

60 

70 

100 

140 

50 

70 

90 

20-90 

600-750 

200-350 

100-110 

40-60 

30-60 

5-10 

20-60 



of the cut; the tendency of the work to spring 
away from the tool; and the rigidity and power 
of the lathe. Since conditions vary, it is good 
practice to find out what the tool and work will 
stand, and then select the most practical and 
efficient speed and feed consistent with the finish 
desired. 

If the cutting speed is too slow, the job takes 
longer than necessary and the work produced is 



8-15 



often unsatisfactory because of a poor finish. 
On the other hand, if the speed is too fast 
the tool edge will dull quickly and will require 
frequent regrinding. The cutting speeds possible 
are greatly affected by the use of a suitable 
cutting lubricant. For example, steel that can 
be rough turned dry at 60 rpm can be turned 
at about 80 rpm when flooded with a good 
cutting lubricant. 

When ROUGHING parts down to size, 
use the greatest depth of cut and feed per 
revolution that the work, the machine, and 
the tool will stand at the highest practical 
speed. On many pieces, when tool failure is 
the limiting factor in the size of the roughing 
cut, it is usually possible to reduce the speed 
slightly and increase the feed to a point that 
the metal removed is much greater. This will 
prolong tool life. Consider an example of when 
the depth of cut is 1/4 inch, the feed is 20 
thousandths of an inch per revolution, and the 
speed is 80 fpm. If the tool will not permit 
additional feed at this speed, you can usually drop 
the speed to 60 fpm and increase the feed to about 
40 thousandths of an inch per revolution without 
having tool trouble. The speed is therefore 
reduced 25% but the feed is increased 100% . The 
actual time required to complete the work is less 
with the second setup. 

On the FINISH TURNING OPERATION, a 

very light cut is taken since most of the stock has 
been removed on the roughing cut. A fine feed 
can usually be used, making it possible to run a 
high surface speed. A 50% increase in speed 
over the roughing speed is commonly used. In 
particular cases, the finishing speed may be twice 
the roughing speed. In any event, run the work 
as fast as the tool will withstand to obtain the 
maximum speed in this operation. Use a sharp 
tool to finish turning. 



Cutting Lubricant 

A cutting lubricant serves two main purposes: 
(1) It cools the tool by absorbing a portion of the 
heat and reduces the friction between the tool and 
the metal being cut. (2) It keeps the cutting edge 
of the tool flushed clean. A cutting lubricant 
generally allows you to use a higher cutting speed, 
heavier feeds, and depths of cut than if you 
performed the machining operation dry. The life 
of the cutting tool is also prolonged by lubricants. 



Some common materials and their cutting 
lubricants are as follows: 

Cast iron usually worked dry or with a 
soluble oil mixture of 1 part of oil to 30 parts 
of water, or mineral lard oil. 

Alloy steel soluble oil mixture of 1 part of 
oil to 10 parts of water, or mineral lard oil. 

Low/medium carbon steel soluble oil 
mixture of 1 part of oil to 20 parts of water, 
or mineral lard oil. 

Brasses and bronzes soluble oil mixture of 
1 part of oil to 20 parts of water, or mineral 
lard oil. 

Stainless steel soluble oil mixture of 1 part 
of oil to 5 parts of water, or mineral lard oil. 

Aluminum soluble oil mixture of 1 part of 
oil to 25 parts of water, or dry. 

Nickel alloys/Monel soluble oil mixture of 
1 part of oil to 20 parts of water, or a 
sulfur /based oil. 

Babbitt dry or with a mixture of mineral lard 
oil and kerosene. 

While the use of a lubricant for straight turn- 
ing is desirable, it is very important for threading. 
The various operations used and materials 
machined on a lathe may cause problems in the 
selection of the proper lubricant. A possible 
solution is to select a lubricant that is suitable for 
the majority of the materials you plan to work 
with. 

Chatter 

A symptom of improper lathe operation is 
known as "chatter." Chatter is vibration in either 
the tool or the work. The finished work surface 
will appear to have a grooved or lined finish 
instead of the smooth surface that is expected. The 
vibration is set up by a weakness in the work, 
work support, tool, or tool support and is perhaps 
the most elusive thing you will find in the entire 
field of machine work. As a general rule, 
strengthening the various parts of the tool 
support train will help. It is also advisable to 
support the work with a center rest or follower 
rest. 



8-16 



excessive. Since excessive speed is probably the 
most frequent cause of chatter, reduce the speed 
and see if the chatter stops. You may also increase 
the feed, particularly if you are taking a rough 
cut and the finish is not important. Another 
adjustment you can try is to reduce the lead angle 
of the tool (the angle formed between the surface 
of the work and the side cutting edge of the tool). 
You may do this by positioning the tool closer 
and perpendicular to the work. 

If none of the above actions works, examine 
the lathe and its adjustments. Gibs may be loose 
or bearings may be worn after a long period of 
heavy service. If the machine is in perfect 
condition, the fault may be in the tool or the tool 
setup. Check to be sure the tool has been properly 
sharpened to a point or as near to a point as the 
specific finish will permit. Reduce the overhang 
of the tool as much as possible and recheck the 
gib and bearing adjustments. Finally, be sure that 
the work is properly supported and that the 
cutting speed is not too high. 

Direction of Feed 

Regardless of how the work is held in the 
lathe, the tool should feed toward the headstock. 
This causes most of the pressure of the cut to be 
exerted on the workholding device and the 
spindle thrust bearings. When you must feed the 
cutting tool toward the tailstock, take lighter cuts 
at reduced feeds. In facing, the general practice 
is to feed the tool from the center of the workpiece 
toward the periphery. 

FACING 

Facing is the machining of the end surfaces 
and shoulders of a workpiece. In addition to 
squaring the ends of the work, facing will let you 
accurately cut the work to length. Generally, in 
facing the workpiece you will need to take only 
light cuts since the work has already been cut to 
approximate length or rough machined to the 
shoulder. 

Figure 8-25 shows how to face a cylindrical 
piece. Place the work on centers and install a dog. 
Using a right-hand side tool, take one or two light 
cuts from the center outward to true the work. 

If both ends of the work must be faced, 
reverse the piece so the dog drives the end just 
faced. Use a steel ruler to layout the required 
length, measuring from the faced end to the end 




SIDE VIEW 



28.129X 



Figure 8-25. Right-hand side tool. 



to be faced. After you ensure that there is no burr 
on the finished end to cause an inaccurate 
measurement, mark off the desired dimension 
with a scribe and face the second end. 

Figure 8-26 shows the facing of a shoulder 
having a fillet corner. First, take a finish cut on 
the outside of the smaller diameter section. Next 
machine the fillet with a light cut by manipulating 
the apron handwheel and the crossfeed handle in 
unison to produce a smooth rounded surface. 
Finally, use the tool to face from the fillet to the 
outside diameter of the work. 

In facing large surfaces, lock the carriage in 
position since only cross feed is required to 
traverse the tool across the work. With the 
compound rest set at 90 (parallel to the axis of 
the lathe), use the micrometer collar to feed the 
tool to the proper depth of cut in the face. For 
greater accuracy in getting a given size when 
finishing a face, set the compound rest at 30 . In 
this position, .001-inch movement of the 
compound rest will move the tool exactly 
.0005-inch in a direction parallel to the axis of the 
lathe. (In a 30 - 60 right triangle, the length of 
the side opposite the 30 angle is equal to one- 
half of the length of the hypotenuse.) 





28.130X 



Figure 8-26. Facing a shoulder. 



8-17 



TURNING 

Turning is the machining of excess stock from 
the periphery of the workpiece to reduce the 
diameter. Bear in mind that the diameter of the 
work being turned is reduced by the amount equal 
to twice the depth of the cut; thus, to reduce the 
diameter of a piece by 1/4 inch, you must remove 
1/8 inch of metal from the surface. 

To remove large amounts of stock in most 
lathe machining, you will take a series of roughing 
cuts to remove most of the excess stock and then 
a finishing cut to accurately "size" the workpiece. 



Rough Turning 

Figure 8-27 illustrates a lathe taking a heavy 
cut. This is called rough turning. When a great 
deal of stock is to be removed, you should take 
heavy cuts in order to complete the job in the least 
possible time. 

Be sure to select the proper tool for taking a 
heavy chip. The speed of the work and the amount 
of feed of the tool should be as great as the tool 
will stand. 

When taking a roughing cut on steel, cast iron, 
or any other metal that has a scale on its surface, 
be sure to set the tool deeply enough to get under 
the scale in the first cut. If you do not, the scale 
on the metal will dull the point of the tool. 




Rough machine the work to almost the 
finished size; then be very careful in taking 
measurements on the rough surface. 

Often the heat produced during rough turning 
will expand the workpiece, and the lubricant will 
flow out of the live center hole. This will result 
in both the center and the center hole becoming 
worn. Always check the center carefully and 
adjust as needed during rough turning operations. 

Figure 8-28 shows the position of the tool for 
taking a heavy chip on large work. Set the tool 
so that if anything causes it to change position 
during the machining operation, the tool will 
move away from the work, thus preventing 
damage to the work. Also, setting the tool in this 
position may prevent chatter. 

Finish Turning 

When you have rough turned the work to 
within about 1/32 inch of the finished size, take 
a finishing cut. A fine feed, the proper lubricant, 
and above all a keen-edged tool are necessary to 
produce a smooth finish. Measure carefully to be 
sure you are machining the work to the proper 
dimension. Stop the lathe whenever you take any 
measurements. 

If you must finish the work to extremely close 
tolerances, wait until the piece is cool before 
taking the finish cut. If the piece has expanded 
slightly because of the heat generated by turning 
and you turn it to size while it is hot, the piece 
will be undersize after it has cooled and 
contracted. 

If you plan to finish the work on a cylindrical 
grinder, leave the stock slightly oversize to allow 
for the metal the grinder will remove. 

Perhaps the most difficult operation for a 
beginner in machine work is taking accurate 
measurements. So much depends on the accuracy 



s, 



28.131X 



Figure 8-27. Rough turning. 



28.132X 
Figure 8-28. Position of tool for heavy cut. 



instruments. You will develop a certain "feel" 
through experience. Do not be discouraged if your 
first efforts do not produce perfect results. 
Practice taking measurements on pieces of known 
dimensions. You will acquire the skill if you are 
persistent. 

Turning to a Shoulder 

A time saving procedure for machining a 
shoulder is illustrated in figure 8-29. First, locate 
and scribe the exact location of the shoulder on 
the work. Next, use a parting tool to machine a 
groove 1/32 inch from the scribe line toward the 
smaller finish diameter end and 1/32 larger than 
the smaller finish diameter. Then take heavy cuts 
up to the shoulder made by the parting tool. 
Finally, take a finish cut from the small end to 
the shoulder scribe line. This procedure eliminates 
detailed measuring and speeds up production. 



PARTING AND GROOVING 

One of the methods of cutting off a piece of 
stock while it is held in a lathe is a process called 
parting. This process uses a specially shaped tool 
with a cutting edge similar to that of a square nose 
tool. The parting tool is fed into the rotating 
work, perpendicular to its axis, cutting a 
progressively deeper groove as the work rotates. 
When the cutting edge of the tool gets to the center 
of the work being parted, the work drops off as 
if it were sawed off. Parting is used to cut off parts 
that have already been machined in the lathe or 
to cut tubing and bar stock to required lengths. 

Parting tools can be the inserted blade type 
or can be ground from a standard tool blank. 





of the cutting portion of the blade that extends 
from the holder should be only slightly greater 
than half the diameter of the work to parted. The 
end cutting edge of the tool must feed directly 
toward the center of the workpiece. To ensure 
this, place a center in the tailstock and align the 
parting tool vertically with the tip of the center. 
The chuck should hold the work to be parted with 
the point at which the parting is to occur as close 
as possible to the chuck jaws. Always make the 
parting cut at a right angle to the centerline of 
the work. Feed the tool into the revolving work 
with the cross-slide until the tool completely 
separates the work. 

Cutting speeds for parting are usually slower 
than turning speeds. You should use a feed that 



STRAIGHT HOLDER 




INSERTED 
BLADE 

RIGHT HAND 
OFFSET 




A. HOLDERS 




OFFSET 



28.133X 



Figure 8-29. Machining to a shoulder. 



B. TOOL OFFSET 
Figure 8-30. Parting tools. 



8-19 



will keep a thin chip coming from the work. If 
chatter occurs, decrease the speed and increase the 
feed slightly. If the tool tends to gouge or dig in, 
decrease the feed. 

Grooves are machined in shafts to provide for 
tool runout in threading to a shoulder, to allow 
clearance for assembly of parts, to provide 
lubricating channels, or to provide a seating 
surface for seals and O-rings. Square, round, and 
"V" grooves and the tools which are used to 
produce them are shown in figure 8-31. 

The grooving tool is a type of forming tool. 
It is ground without side rake or back rake and 
is set to the work at center height with a minimum 
of overhang. The side and end relief angles are 
generally somewhat less than for turning tools. 
When you machine a groove, reduce the spindle 
speed to prevent chatter which often develops at 
high speeds because of the greater amount of tool 
contact with the work. 

DRILLING AND REAMING 

Drilling operations performed in a lathe differ 
very little from drilling operations performed in 
a drilling machine. For best results, start the drill- 
ing operation by drilling a center hole in the work, 
using a combination center drill and countersink. 
The combination countersink-center drill is held 
in a drill chuck which is mounted in the tailstock 
spindle. After you have center drilled the work, 
replace the drill chuck with a taper shank drill. 
(Note: BEFORE you insert any tool into the 
tailstock spindle inspect the shank of the tool for 
burrs. If the shank is burred, remove the burrs 
with a handstone.) Feed the drill into the work 
by using the tailstock handwheel. Use a 
coolant/lubricant whenever possible and maintain 
sufficient pressure on the drill to prevent chatter, 
but not enough to overheat the drill. 

If the hole is quite long, back the drill out 
occasionally to clear the flutes of metal chips. 
Large diameter holes may require you to drill a 
pilot hole first. This is done with a drill that is 
smaller than the finished diameter of the hole. 





SQUARE 
GROOVE 



ROUND [_] "V 

GROOVE/O GROOVE 



Figure 8-31. Three common types of grooves. 



After you have drilled the pilot hole to the 
proper depth, enlarge the hole with the finish drill. 
If you plan to drill the hole completely through 
the work, slow down the feed as the drill nears 
the hole exit. This will produce a smoother exit 
hole by causing the drill to take a finer cut as it 
exits the hole. 

If the twist drill is not ground correctly, the 
drilled hole will be either excessively oversized or 
out of round. Check the drill for the correct angle, 
clearance, cutting edge lengths and straightness 
before setting it up for drilling. It is almost 
impossible to drill a hole exactly the same size as 
the drill regardless of the care taken in ensuring 
an accurately ground drill and the proper selection 
of speeds and feeds. For this reason, any job 
which requires close tolerances or a good finish 
on the hole should be reamed or bored to the 
correct size. 

If the job requires that the hole be reamed, 
it is good practice to first take a cleanup cut 
through the hole with a boring tool. This will true 
up the hole for the reaming operation. Be sure 
to leave about 1/64 inch for reaming. The 
machine reamer has a taper shank and is held in 
and fed by the tailstock. To avoid overheating the 
reamer, set the work speed at about half that used 
for the drilling operation. During the reaming 
operation, keep the reamer well lubricated. This 
will keep the reamer cool and also flush the chips 
from the flutes. Do not feed the reamer too fast; 
it may tear the surface of the hole and ruin the 
work. 

BORING 

Boring is the machining of holes or any 
interior cylindrical surface. The piece to be bored 
must have a drilled or core hole, and the hole must 
be large enough to insert the tool. The boring 
process merely enlarges the hole to the desired size 
or shape. The advantage of boring is that you get 
a perfectly true round hole. Also, you can bore 
two or more holes of the same or different 
diameters at one setting, thus ensuring absolute 
alignment of the axis of the holes. 

It is usual practice to bore a hole to within a 
few thousandths of an inch of the desired size and 
then to finish it to the exact size with a reamer. 

Work to be bored may be held in a chuck, 
bolted to the faceplate, or bolted to the carriage. 
Long pieces must be supported at the free end of 
a center rest. 

When the boring tool is fed into the hole in 
work being rotated on a chuck or faceplate, the 



nuin nit iiioiuc. me cuiiing cugc ui me uuimg 

tool resembles that of a turning tool. Boring tools 
may be the solid forged type or the inserted cutter 
bit type. 

When the work to be bored is clamped to the 
top of the carriage, a boring bar is held between 
centers and driven by a dog. The work is fed to 
the tool by the automatic longitudinal feed of the 
i carriage. Three types of boring bars are shown 
in figure 8-32. Note the countersunk center holes 
at the ends to fit the lathe centers. 

Part A of figure 8-32 shows a boring bar fitted 
with a fly cutter held by a headless setscrew. The 
other setscrew, bearing on the end of the cutter, 
is for adjusting the cutter to the work. 

Part B of figure 8-32 shows a boring bar fitted 
with a two-edge cutter held by a taper key. This 
is more of a finishing or sizing cutter, as it cuts 
on both sides and is used for production work. 

The boring bar shown in part C of figure 8-32 
is fitted with a cast iron head to adapt it for 
boring work of large diameter. The head is fitted 
with a fly cutter similar to the one shown in part 
A. The setscrew with the tapered point adjusts the 
cutter to the work. 

Figure 8-33 shows a common type of boring 
bar holder and applications of the boring bar for 
boring and internal threading. When threading 
is to be done in a blind hole, it sometimes becomes 






Figure 8-32. Various boring bars. 



28.135 
Figure 8-33. Application of boring bar holder. 



necessary to undercut or relieve the bottom of the 
hole. This will enable mating parts to be screwed 
all the way to the shoulder and make the threading 
operation much easier to do. 



KNURLING 

Knurling is the process of rolling or squeezing 
impressions into the work with hardened steel 
rollers that have teeth milled into their faces. 
Examples of the various knurling patterns are 
shown in chapter 7, figure 7-22. Knurling provides 
a gripping surface on the work; it is also used for 
decoration. Knurling increases the diameter of the 
workpiece slightly when the metal is raised by the 
forming action of the knurl rollers. 

The knurling tool (fig. 7-23) is set up so the 
faces of the rollers are parallel to the surface of 
the work and with the upper and lower rollers 
equally spaced above and below the work axis or 
centerline. The spindle speed should be about half 
the roughing speed for the type of metal being 
machined. The feed should be between 0.015 inch 
and 0.025 inch per revolution. The work should 



8-21 



be rigidly mounted in the tailstock to help offset 
the pressure exerted by the knurling operation. 

The actual knurling operation is simple if you 
follow a few basic rules. The first step is to make 
sure that the rollers in the knurling tool turn freely 
and are free of chips and imbedded metal between 
the cutting edges. During the knurling process, 
apply an ample supply of oil at the point of 
contact to flush away chips and provide lubrica- 
tion. Position the carriage so that 1/3 to 1/2 of 
the face of the rollers extends beyond the end of 
the work. This eliminates part of the pressure 
required to start the knurl impression. Force the 
knurling rollers into contact with the work. 
Engage the spindle clutch. Check the knurl to see 
if the rollers have tracked properly, as shown in 
figure 8-34, by disengaging the clutch after the 
work has revolved 3 or 4 times and by backing 
the knurling tool away from the work. 

If the knurls have double tracked, as shown 
in figure 8-34, move the knurling tool to a new 
location and repeat the operation. If the knurl is 
correctly formed, engage the spindle clutch and 
the carriage feed. Move the knurling rollers 
into contact with the correctly formed knurled 
impressions. The rollers will align themselves with 
the impressions. Allow the knurling tool to feed 
to within about 1/32 inch of the end of the surface 
to be knurled. Disengage the carriage feed and 
with the work revolving, feed the carriage by hand 
to extend the knurl to the end of the surface. Force 
the knurling tool slightly deeper into the work, 
reverse the direction of feed and engage the 
carriage feed. Allow the knurling tool to feed until 
the opposite end of the knurled surface is reached. 
Never allow the knurls to feed off the surface. 

Repeat the knurling operation until the 
diamond impressions converge to a point. Passes 
made after the correct shape is obtained will result 
in stripping away the points of the knurl. Clean 



DOUBLE 
IMPRESSION 



NCORRECT 




the knurl with a brush and remove any burrs or 
sharp edges with a file. When knurling, do not 
let the work rotate while the tool is in contact with 
it if the feed is disengaged. This will cause 
rings to be formed on the surface, as shown in 
figure 8-35. 

SETTING UP THE 
TOOLPOST GRINDER 

The toolpost grinder is a portable grinding 
machine that can be mounted on the compound 
rest of a lathe in place of the toolpost. It can be 
used to machine work that is too hard to cut by 
ordinary means or to machine work that requires 
a very fine finish. Figure 8-36 shows a typical 
toolpost grinder. 

The grinder must be set on center, as shown 
in figure 8-37. The centering holes located on the 
spindle shaft are used for this purpose. The 
grinding wheel takes the place of a lathe cutting 
tool; it can perform most of the same operations 
as a cutting tool. Cylindrical, tapered, and 
internal surfaces can be ground with the toolpost 
grinder. Very small grinding wheels are mounted 
on tapered shafts, known as quills, to grind 
internal surfaces. 

The grinding wheel speed is changed by using 
various sizes of pulleys on the motor and spindle 
shafts. An instruction plate on the grinder gives 
both the diameter of the pulleys required to 
obtain a given speed and the maximum safe speed 
for grinding wheels of various diameters. Grinding 
wheels are safe for operation at a speed just below 
the highest recommended speed. A higher than 
recommended speed may cause the wheel to 
disintegrate. For this reason, wheel guards are 
furnished with the toolpost grinder to protect 
against injury. 

Always check the pulley combinations given 
on the instruction plate of the grinder when 




CORRECT 
IMPRESSION 



RINGS ON WORK CAUSED BY STOPPING 
TOOL TRAVEL WITH WORK REVOLVING 



Figure 8-34, Knurled impressions. 



Figure 8-35. Rings on a knurled surface. 



BELT 



BELT 
GUARD 




SPINDLE 



CLAMP 
Figure 8-36. Toolpost grinder. 



WHEEL 
GUARD 



GRINDING 
WHEEL 



TOOL POST GRINDER SPINDLE 



HEADSTOCK 
SPINDLE 




Figure 8-37. Mounting the grinder at center height. 



you mount a wheel. Be sure that the combination 
is not reversed, because this may cause the 
wheel to run at a speed far in excess of that 
recommended. During all grinding operations, 
wear goggles to protect your eyes from flying 
abrasive material. 

Before you use the grinder, dress and true the 
wheel with a diamond wheel dresser. The dresser 
is held in a holder that is clamped to the chuck 
or faceplate of the lathe. Set the point of the 
diamond at center height and at a 10 to 1 5 angle 
in the direction of the grinding wheel rotation, 
as shown in figure 8-38. The 10 to 15 angle 
prevents the diamond from gouging the wheel. 
Lock the lathe spindle by placing the spindle speed 
control lever in the low rpm position. (Note: The 
lathe spindle does not revolve when you are 
dressing the grinding wheel.) 




Figure 8-38. Position of the diamond dresser. 



Bring the grinding wheel into contact with the 
diamond dresser by carefully feeding the cross- 
slide in by hand. Move the wheel slowly by hand 
back and forth over the point of the diamond, 
taking a maximum cut of .0002 inch. Move the 
carriage if the face of the wheel is parallel to the 
ways of the lathe. Move the compound rest if the 
face of the wheel is at an angle. Make the final 
depth of cut of 0.0001 inch with a slow, even feed 
to obtain a good wheel finish. Remove the 
diamond dresser holder as soon as you finish 
dressing the wheel and adjust the grinder to begin 
the grinding operation. 

Rotate the work at a fairly low speed during 
the grinding operation. The recommended surface 
speed is 60 to 100 feet per minute (fpm). The depth 
of cut depends upon the hardness of the work, 
the type of grinding wheel, and the desired finish. 
Avoid taking grinding cuts deeper than 0.002 inch 
until you gain experience. Use a fairly low rate 
of feed. You will soon be able to judge whether 
the feed should be increased or decreased. Never 
stop the work or the grinding wheel while they 
are in contact with each other. 

To refinish a damaged lathe center, as shown 
in figure 8-5, first ensure that the spindle holes, 
drill sleeves, and centers are clean and free of 
burrs. Install the lathe center to be refinished in 
the headstock. Next, position the compound rest 
parallel to the ways; then, mount the toolpost 
grinder on the compound rest. Make sure that 
the grinding wheel spindle is at center height 
and aligned with the lathe centers. Move the 
compound rest 30 to the right of the lathe spindle 
axis, as shown in figure 8-5. Mount the wheel 
dresser, covering the ways and carriage with rags 
to protect them from abrasive particles. Wear gog- 
gles to protect your eyes. 

Start the grinding motor, by alternately 
turning it on and off (let it run a bit longer each 



8-23 



time) until the abrasive wheel is brought up to top 
speed. Dress the wheel, feeding the grinder with 
the compound rest. Then move the grinder clear 
of the headstock center and remove the wheel 
dresser. Set the lathe for the desired spindle speed 
and engage the spindle. Pick up the surface of the 
center. Take a light depth of cut and feed the 
grinder back and forth with the compound rest. 
Do not allow the abrasive wheel to feed entirely 
off the center. Continue taking additional cuts 
until the center cleans up. To produce a good 
finish, reduce the feed rate and the depth of cut 
to .0005 inch. Grind off the center's sharp point, 
leaving a flat with a diameter about 1/32 inch. 
Move the grinder clear of the headstock and turn 
it off. 

Figure 8-39 illustrates refacing the seat of a 
high-pressure steam valve which has a hard, 
Stellite-faced surface. The refacing must be done 
with a toolpost grinder. Be sure that all inside 
diameters run true before starting the machine 
work. Spindle speed of the lathe should be about 
40 rpm or less. Too high a speed will cause the 
grinding wheel to vibrate. Set the compound rest 
to correspond with the valve seat angle. Use the 
cross-slide hand feed or the micrometer stop on 
the carriage for controlling the depth of cut; use 
the compound rest for traversing the grinding 




28.136 
Figure 8-39. Refacing seat of high-pressure steam valve. 



wheel across the work surface. Remember, 
whenever you grind on a lathe, always place a 
cloth across the ways of the bed and over any 
other machined surfaces that could become 
contaminated from grinding dust. 



8-24 



CHAPTER 9 

ADVANCED ENGINE LATHE OPERATIONS 



In chapter 8 you studied a number of lathe 
operations, the various methods of holding and 
centering work on the engine lathe, and how to 
set lathe tools. This chapter is a continuation 
of engine lathe operations and deals primarily 
with cutting tapers, boring, and cutting screw 
threads. 



TAPERS 

Taper is the gradual decrease in the diameter 
of thickness of a piece of work toward one end. 
To find the amount of taper in any given length 
of work, subtract the size of the small end from 
the size of the large end. Taper is usually expressed 
as the amount of taper per foot of length, or as 
an angle. The following examples explain how to 
determine taper per foot of length. 

EXAMPLE 1 : Find the taper per foot of a 
piece of work 2 inches long: Diameter of the 
small end is 1 inch; diameter of the large end is 
2 inches. 

The amount of the taper is 2 inches minus 1 
inch, which equals 1 inch. The length of the taper 
is given as 2 inches. Therefore, the taper is 1 inch 
in 2 inches of length. In 12 inches of length it 
would be 6 inches. (See fig. 9-1). 

EXAMPLE 2: Find the taper per foot of a 
piece 6 inches long. Diameter of the small 
end is 1 inch; diameter of the large end is 
2 inches. 

The amount of taper is the same as in 
example 1; that is, 1 inch. (See fig. 9-1). 
However, the length of this taper is 6 inches; hence 
the taper per foot is 1 inch x 12/6 = 2 inches per 
foot. 

From the foregoing, you can see that the 
length of a tapered piece is very important in 
computing the taper. If you bear this in mind 



oof ..,--- 




Figure 9-1. Tapers. 

when machining tapers, you will not go wrong. 
Use the formula: 

TPF = TPI x 12 

where: 

TPF = TAPER PER FOOT 

TPI = TAPER PER INCH 

Other formulas used in figuring tapers are as 
follows: 

T 

TPT = 
1F1 L 

where: 

TPI = TAPER PER INCH 

T = TAPER (Difference between large and 
small diameters, expressed in inches 

L = LENGTH of taper, expressed in inches 
x 



T = 



and T = TPI x L (in inches) 



TPI = 



TPF 
12 



9-1 



Tapers are frequently cut by setting the angle 
of the taper on the appropriate lathe attachment. 
There are two angles associated with a taper 
the included angle and the angle with the center 
line. The included angle is the angle between the 
two angled sides of the taper. The angle with the 
center line is the angle between the center line and 
either of the angled sides. Since the taper is turned 
about a center line, the angle between one side 
and the center line is always equal to the angle 
between the other side and the center line. 
Therefore, the included angle is always twice the 
angle with the center line. The importance of this 
relationship will be shown later in this chapter. 
Table 9-1 is a machinist's chart showing the 
relationship between taper per foot, included 
angle, and angle with the center line. 

There are several well-known tapers that are 
used as standards for machines on which they are 
used. These standards make it possible to make 
or get parts to fit the machine in question without 
detailed measuring and fitting. By designating the 
name and number of the standard taper being 
used, you can immediately find the length, the 
diameter of the small and large ends, the taper 
per foot, and all other pertinent measurements in 
appropriate tables found in most machinist's 
handbooks. 



There are three standard tapers with which you 
should be familiar: (1) the MORSE TAPER 
(approximately 5/8 inch per foot) used for the 
tapered holes in lathe and drill press spindles and 
the attachments that fit them, such as lathe 
centers, drill shanks, and so on; (2) the BROWN 
& SHARPE TAPER (1/2 inch per foot, except 
No. 10, which is 0.5161 inch per foot) used for 
milling machine spindle shanks; and (3) the 
JARNO TAPER (0.600 inch per foot) used by 
some manufacturers because of the ease with 
which its dimensions can be determined: 

T^- * n j taper number 

Diameter of large end = 5 - 

TV t u A taper number 

Diameter of small end = - - 



T . . 
Length of taper = 



taper number 
- 



Two additional tapers that are considered 
standard are the tapered pin and pipe thread 
tapers. Tapered pins have a taper of 1/4 inch per 
foot while tapered pipe threads have a taper of 
3/4 inch per foot. 

A copy of a Morse taper table is shown in 
figure 9-2. You will no doubt have more use for 
this taper than any other standard taper. 



Table 9-1. Tapers Per Foot/ Angles 



Taper per 
foot 


Angle included 


Angle with centerline 


Taper per inch 


1/8 


Degrees 


1 
1 
1 
2 
2 
2 
3 
3 
3 
3 
4 
4 
4 
9 


Minutes 
36 
54 
12 
30 
47 
5 
23 
41 

17 
35 
53 
11 
28 
46 
32 


Degrees 





1 
1 
1 
1 
1 
1 
1 
2 
2 
2 
4 


Minutes 
18 
27 
36 
45 
54 
3 
12 
21 
30 
38 
47 
56 
5 
14 
23 
46 


Inches 
0.01042 
.01563 
.02083 
.02604 
.03125 
.03646 
.04167 
.04688 
.05208 
.05729 
.06250 
.06771 
.07292 
.07813 
.08333 
. 16667 


3/16 


1/4 


5/16 
3/8 


7/16 


1/2 


9/16 


5/8 


11/16. . . . 
3/4 


13/16 .... 
7/8 


15/16. . . . 
1 


2 





9-2 





Key 8<> 19'= 
Taper 1H in 12 



Y&/A 



DETAIL DIMENSIONS 



Number of Taper 





1 


2 


3 


4 


5 


6 


7 


Diameter of plug at small end . . D 
Diameter at end of socket .... A 
Shank: 
Whole length of shank B 


0.252 
.3561 

2-11/32 
2-7/32 
2-1/32 
2 

5/32 
1/4 
.235 

.160 
9/16 
1-15/16 
.625 
.05208 



0.369 

.475 

2-9/16 
2-7/16 
2-3/16 
2-1/8 

13/64 
3/8 
.343 

.213 

3/4 
2-1/16 
.600 
.05 
1 


0.572 
.700 

3-1/8 
2-15/16 
2-5/8 
2-9/16 

1/4 
7/16 
17/32 

.260 

7/8 
2-1/2 
.602 
.05016 
2 


0.778 
.938 

3-7/8 
3-11/16 
3-1/4 
3-3/16 

5/16 
9/16 
23/32 

.322 

1-3/16 
3-1/16 
.602 
.05016 
3 


1.020 
1.231 

4-7/8 
4-5/8 
4-1/8 
4-1/16 

15/32 
5/8 
31/32 

.478 
1-1/4 
3-7/8 
.623 
.05191 
4 


1.475 
1.748 

6-1/8 
5-7/8 
5-1/4 
5-3/16 

5/8 
3/4 
1-13/32 

.635 
1-1/2 
4-15/16 
.630 
.0525 
5 


2.116 
2.494 

8-9/16 
8-1/4 
7-3/8 
7-1/4 

3/4 
1-1/8 
2 

.760 
1-3/4 
7 
.626 
.05216 
6 


2.750 
3.270 

11-5/8 
11-1/4 
10-1/8 
10 

1-1/8 
1-3/8 
2-5/8 

1.135 
2-5/8 
9-1/2 
.625 
.05208 
7 


Shank depth S 


Depth of hole H 


Standard plug depth P 


Tongue: 
Thickness of tongue t 


Length of tongue T 


Diameter of tongue d 


Keyway: 
Width of keyway . . . W 


Length of keyway L 


End of socket to keyway K 


Taper per foot 


Taper per inch 


Number of key 



28.138X 



Figure 9-2. Morse tapers. 



METHODS OF TURNING TAPERS 

In ordinary straight turning, the cutting tool 
moves along a line parallel to the axis of the work, 
causing the finished job to be the same diameter 
throughout. If, however, in cutting, the tool 
moves at an angle to the axis of the work, a taper 
will be produced. Therefore, to turn a taper, you 
must either mount the work in the lathe so the 
axis on which it turns is at an angle to the axis 
of the lathe, or cause the cutting tool to move at 
an angle to the axis of the lathe. 



There are three methods in common use for 
turning tapers: 

1. SET OVER THE TAILSTOCK, which 
moves the dead center away from the axis of 
the lathe and causes work supported between 
centers to be at an angle with the axis of the 
lathe. 

2. USE THE COMPOUND REST set at 
an angle, which causes the cutting tool to be 
fed at the desired angle to the axis of the 
lathe. 



3. USE THE TAPER ATTACHMENT, 

which also causes the cutting tool to move at an 
angle to the axis of the lathe. 

In the first method, the cutting tool is fed by 
the longitudinal feed parallel to the lathe axis, but 
a taper is produced because the work axis is at 
an angle. In the second and third methods, the 
work axis coincides with the lathe axis, but a taper 
is produced because the cutting tool moves at an 
angle. 

Setting Over the Tailstock 

As stated in chapter 7, you can move the 
tailstock top sideways on its base by using the 
adjusting screws. In straight turning you use these 
adjusting screws to align the dead center with the 
tail center by moving the tailstock to bring it on 
the center line of the spindle axis. For taper 
turning, you deliberately move the tailstock off 
center, and the amount you move it determines 
the taper produced. You can approximate the 
amount of setover by using the zero lines inscribed 
on the base and top of the tailstock as shown in 
figure 9-3. Then for final adjustment, measure the 
setover with a scale between center points as 
illustrated in figure 9-4. 

In turning a taper by this method, the distance 
between centers is of utmost importance. To 
illustrate, figure 9-5 shows two very different 
tapers produced by the same amount of setover 
of the tailstock, because for one taper the length 
of the work between centers is greater than for 
the other. THE CLOSER THE DEAD CENTER 
IS TO THE LIVE CENTER, THE STEEPER 
WILL BE THE TAPER PRODUCED. Suppose 






28.140X 
Figure 9-4. Measuring setover of dead center. 




28.141X 

Figure 9-5. Setover of tailstock showing importance of 
considering length of work. 



you want to turn a taper on the full length of a 
piece 12 inches long with one end having a 
diameter of 3 inches, and the other end a diameter 
of 2 inches. The small end is to be 1 inch smaller 
than the large end; so you set the tailstock over 
one-half of this amount or 1/2 inch in this 
example. Thus, at one end the cutting tool will 
be 1/2 inch closer to the center of the work than 
at the other end; so the diameter of the finished 
job will be 2 x 1/2 or 1 inch less at the small end. 
Since the piece is 12 inches long, you have 
produced a taper of 1 inch per foot. Now, if you 
wish to produce a taper of 1 inch per foot on a 
piece only 6 inches long, the small end will be only 
1/2 inch less in diameter than the larger end, so 
you should set over the tailstock 1/4 inch or one- 
half of the distance used for the 12-inch length. 
By now you can see that the setover is 
proportional to the length between centers. 
Setover is computed by using the following 
formula: 

S -lx^ 

S - 2 X 12 

where: 

S = setover in inches 

T = taper per foot in inches 

L *= length of taper in inches 



28.139X 
Figure 9-3. Tailstock setover lines for taper turning. 



T = length in feet of taper 



a mandrel, L is the length of the mandrel between 
centers. You cannot use the setover tailstock 
method for steep tapers because the setover would 
be too great and the work would not be properly 
supported by the lathe centers. The bearing 
surface becomes less and less satisfactory as the 
setover is increased. CAUTION: DO NOT 
EXCEED .250-inch setover. 

After turning a taper by the tailstock setover 
method, do not forget to realign the centers for 
straight turning of your next job. 



Using the Compound Rest 

The compound rest is generally used for short, 
steep tapers. Set it at the angle the taper will make 
with the center line (that is, half of the included 
angle of the taper). Then feed the tool to the work 
at this angle by using the compound rest feed 
screw. The length of taper you can machine is 
short because the travel of the compound rest is 
limited. 

One example of using the compound rest for 
taper work is the truing of a lathe center. Other 
examples are ref acing an angle type valve disk and 
machining the face of a bevel gear. Such jobs are 
often referred to as working to an angle rather 
than as taper work. 

The graduations marked on the compound 
rest provide a quick means for setting it to the 
angle desired. When the compound rest is set at 
zero, the cutting tool is perpendicular to the lathe 
axis. When the compound rest is set at 90 on 
either side of zero, the cutting tool is parallel to 
the lathe axis. 

To set up the compound rest for taper turning, 
first determine the angle to be cut, measured 
from the center line. This angle is half of the 
included angle of the taper you plan to cut. 
Then set the compound rest to the complement 
of the angle to be cut (90 minus angle 
to be cut). For example, to machine a 50 included 
angle (25 angle with the center line), set the 
compound rest at 90 - 25, or 65. 

When you must set the compound rest very 
accurately, to a fraction of a degree for example, 



to the required angle. Hold the blade of the 
protractor on the flat surface of the faceplate and 
hold the base of the protractor against the finished 
side of the compound rest. 

For turning and boring long tapers with 
accuracy, the taper attachment is indispens- 
able. It is especially useful in duplicating 
work; you can turn and bore identical tapers with 
one setting of the taper guide bar. Set the guide 
bar at an angle to the lathe that corresponds to 
the desired taper. The tool cross slide will be 
moved laterally by a shoe, which slides on the 
guide bar as the carriage moves longitudinally. 
The cutting tool will move along a line parallel 
to the guide bar. The taper produced will have 
the same angular measurement as that set on the 
guide bar. The guide bar is graduated in degrees 
at one end and in inches per foot of taper at the 
other end to provide for rapid setting. Figure 9-6 
is a view of the end that is graduated in inches 
per foot of taper. 

When you prepare to use the taper attach- 
ment, run the carriage up to the approximate 
position of the work to be turned. Set the 
tool on line with the center of the lathe. 
Then bolt or clamp the holding bracket 
to the ways of the bed (the attachment 
itself is bolted to the back of the carriage saddle) 




28.142X 



Figure 9-6. End view of taper guide bar. 



9-5 



bar now controls the lateral movement of the cross 
slide. Set the guide bar for the taper desired; the 
attachment is ready for operation. To make the 
final adjustment of the tool for size, use the 
compound rest feed screw, since the crossfeed 
screw is inoperative. 

There will be a certain amount of lost motion 
or backlash when the tool first starts to feed along 
the work. This is caused by looseness between the 
crossfeed screw and the cross-slide nut. If the 
backlash is not eliminated, a straight portion will 
be turned on the work. You can remove the 
backlash by moving the carriage and tool slightly 
past the start of the cut and then returning the 
carriage and tool to the start of the cut. 

TAPER BORING 

Taper boring is usually done with either the 
compound rest or the taper attachment. The rules 



the boring of taper holes. Begin by drilling the 
hole to the correct depth with a drill of the same 
size as the specified small diameter of the taper. 
This gives you the advantage of boring to the right 
size without having to remove metal at the bottom 
of the bore, which is rather difficult, particularly 
in small, deep holes. 

For turning and boring tapers, set the tool 
cutting edge exactly at the center of the work. 
That is, set the point of the cutting edge even with 
the height of the lathe centers; otherwise, the taper 
may be inaccurate. 

Cut the hole and measure its size and taper 
using a taper plug gauge and the "cut and try" 
method. 

1 . After you have taken one or two cuts, clean 
the bore. 




28.1433 



Figure 9-7. Turning a taper using taper attachment. 



9-6 



l_ 



3. Insert the gauge into the hole and turn it 
SLIGHTLY so the chalk (or prussian blue) rubs 
from the gauge onto the surface of the hole. If 
the workpiece is to be mounted on a spindle, use 
the tapered end of the spindle instead of a gauge 
to test the taper. 

4. Areas that do not touch the gauge will be 
shown by a lack of chalk (or prussian blue). 

5. Continue making minor corrections until 
all, or an acceptable portion, of the hole's 
surface touches the gauge. Be sure the taper 
diameter is correct before you turn the taper to 
its finish diameter. 

Figure 9-8 shows a Morse standard taper plug 
and a taper socket gauge. They not only give the 
proper taper, but also show the proper distance 
that the taper should enter the spindle. 




28.144X 
Figure 9-8. Morse taper socket gauge and plug gauge. 



Much of the machine work performed by a 
Machinery Repairman includes the use of screw 
threads. The thread forms you will be working 
with most are V-form threads, Acme threads, and 
square threads. Each of these thread forms is 
used for specific purposes. V-form threads are 
commonly used on fastening devices such as bolts 
and nuts as well as on machine parts. Acme screw 
threads are generally used for transmitting 
motion, such as between the lead screw and lathe 
carriage. Square threads are used to increase 
mechanical advantage and to provide good 
clamping ability as in the screw jack or vise screw. 
Each of these screw forms is discussed more fully 
later in the chapter. 

There are several terms used in describing 
screw threads and screw thread systems that you 
must know before you can calculate and machine 
screw threads. Figure 9-9 illustrates some of the 
following terms: 

EXTERNAL THREADS: A thread on the 
outside surface of a cylinder. 

INTERNAL THREAD: A thread on the in- 
side surface of a hollow cylinder. 

RIGHT-HAND THREAD: A thread that, 
when viewed axially, winds in a clockwise and 
receding direction. 

LEFT-HAND THREAD: A thread that, 
when viewed axially, winds in a counterclockwise 
and receding direction. 



CREST 
ROOT. 



FLANKS 




60 
THREAD ANGLE 

EXTERNAL THREAD 



Figure 9-9. Screw thread nomenclature. 



9-7 



LEAD: The distance a threaded part moves 
axially in a fixed mating part in one complete 
revolution. 

PITCH: The distance between corresponding 
points on adjacent threads. 

SINGLE THREAD: A single (single start) 
thread whose lead equals the pitch. 

MULTIPLE THREAD: A multiple (multiple 
start) thread whose lead equals the pitch 
multiplied by the number of starts. 

CLASS OF THREADS: A group of threads 
designed for a certain type of fit. Classes of 
threads are distinguished from each other by the 
amount of tolerance and allowance specified. 

THREAD FORM: The view of a thread along 
the thread axis for a length of one pitch. 

FLANK: The side of the thread. 

CREST: The top of the thread (bounded by 
the major diameter on external threads; by the 
minor diameter on internal threads). 

ROOT: The bottom of the thread (bounded 
by the minor diameter on external threads; by the 
major diameter on internal threads). 

THREAD ANGLE: The angle formed by 
adjacent flanks of a thread. 

PITCH DIAMETER: The diameter of an 
imaginary cylinder that is concentric with the 
thread axis and whose periphery passes through 
the thread profile at the point where the widths 
of the thread and the thread groove are equal. The 
pitch diameter is the diameter that is measured 
when the thread is machined to size. A change 
in pitch diameter changes the fit between the 
thread being machined and the mating thread. 

NOMINAL SIZE: The size that is used for 
identification. For example, the nominal size of 
a 1/2-20 thread is 1/2 inch, but its actual size 
slightly smaller to provide clearance. 

ACTUAL SIZE: The measured size. 

BASIC SIZE: The theoretical size. The basic 
size is changed to provide the desired clearance 
or fit. 

MAJOR DIAMETER: The diameter of an 
imaginary cylinder that passes through the crests 
of an external thread or the roots of an internal 
thread. 

MINOR DIAMETER: The diameter of an 
imaginary cylinder that passes through the roots 
of an external thread or the crests of an internal 
thread. 



HEIGHT OF THREAD: The distance from 
the crest to the root of a thread measured along 
a perpendicular to the axis of the threaded piece 
(also called straight depth of thread). 

SLANT DEPTH: The distance from the crest 
to the root of a thread measured along the angle 
forming the side of the thread. 

ALLOWANCE: An intentional difference 
between the maximum material limits of mating 
parts. It is the minimum clearance (positive 
allowance) or maximum interference (negative 
allowance) between such parts. 

TOLERANCE: The total permissible varia- 
tion of a size. The tolerance is the difference 
between the limits of size. 

THREAD FORM SERIES: Threads are made 
in many different shapes, sizes, and accuracies. 
When special threads are required by the product 
designer, he will specify in detail all the thread 
characteristics and their tolerances for production 
information. When a standard thread is selected, 
however, the designer needs only to specify size, 
number of threads per inch, designation of the 
standard series and class of fit. With these 
specifications, all other information necessary for 
production can be obtained from the established 
standard, as published. The abbreviated designa- 
tions for the different series are as follows: 

Abbreviation Full Title of Standard Series 

UNC Unified coarse thread series 

UNF Unified fine thread series 

UNEF Unified extra fine thread series 

NC American National coarse 

thread series 

NF American National fine thread 

series 

NEF American National extra-fine 

thread series 

UN Unified constant pitch series 

including 4, 6, 8, 12, 16, 20, 
28, and 32 threads per inch 

NA American National Acme thread 

series 

NPT American National tapered pipe 

thread series 

NFS American National straight pipe 

thread series 

NH American National hose cou- 

pling thread series 

NS American National Form thread- 

special pitch 

N BUTT National Buttress Thread 



per inch, series symbol, and class symbol, 
in that order. For example, the designation 
1/4-20 UNC-3A specifies a thread with the follow- 
ing characteristics: 

Nominal thread diameter = 1/4 inch 
Number of threads per inch = 20 
Series (Unified coarse) = UNC 
Class = 3 
External thread = A 

Unless the designation LH (left hand) follows the 
class designation, the thread is assumed to be a 
right-hand thread. An example of the designation 
for a left-hand thread is: 1/4-20 UNC-3A-LH. 

V-FORM THREADS 

The three forms of V-threads that you must 
know how to machine are the V-sharp, the 
American National and The American Standard 
unified. All of these threads have a 60 included 
angle between their sides. The V-sharp thread has 
a greater depth than the others and the crest and 
root of this thread have little or no flat. The 
external American Standard unified thread has 
slightly less depth than the external American 
National thread but is otherwise similar. The 
American Standard unified thread is actually a 
modification of the American National thread. 
This modification was made so that the unified 
series of threads, which permits interchangeability 
of standard threaded fastening devices manufac- 
tured in the United States, Canada, and the 
United Kingdom, could be included in the 
threading system used in the United States. The 
Naval Sea Systems Command and naval procure- 
ment activities use American Standard unified 
threading system specifications whenever possible; 
this system is recommended for use by all naval 
activities. 

To cut a V-form screw thread, you need to 
know (1) the pitch of the thread, (2) the straight 
depth of the thread, (3) the slant depth of the 
thread, and (4) the width of the flat at the root 
of the thread. The pitch of a thread is the basis 
for calculating all other dimensions and is equal 
to 1 divided by the number of threads per inch. 
The tap drill size is equal to the thread size minus 
the pitch, or the thread size minus ONE divided 
by the number of threads per inch. 

Tap Drill Size = Thread Size - 



the thread), use the slant-depth to determine how 
far to feed the tool into the work. The point of 
the threading tool must have a flat equal to the 
width of the flat at the root of the thread (external 
or internal thread, as applicable). If the flat at 
the point of the tool is too wide, the resulting 
thread will be too thin. If the flat is too narrow, 
the thread will be too thick. 

The following formulas will provide the 
information you need for cutting V-form threads: 

1. V-SHARP THREAD 

Pitch - or 1 -f- number of threads per 

inch 
Straight Depth of thread = 0.886 x pitch 

2. AMERICAN NATIONAL THREAD 
Pitch = 1 -r number of threads per inch 

or n 

Straight depth of external thread = 0.64952 
x pitch or 0.541266p 

Straight depth of internal thread 
= 0.541266 x pitch or 0.64952p 

Width of flat at point of tool for external 
and internal threads = 0.125 x pitch or 
0.125p 

Slant depth of external thread = 0.750 
x pitch or 0.750p 

Slant depth of internal thread = 0.625 
x pitch or 0.625p 

3. AMERICAN STANDARD UNIFIED 

Pitch =14- number of threads per inch 
or! 
n 

Straight depth of external thread = 0.61343 
inch x pitch or 0.61343p 

Straight depth of internal thread = 0.54127 
inch x pitch or 0.54127p 

Width of flat at root of external thread 
= 0.125 inch x pitch or 0.125p 

Width of flat at crest of external thread 
= 0.125 inch x pitch or 0.125p 

Double height of external thread = 1 .22687 
inch x pitch or 1 .22687p 

Double height of internal thread = 1 .08253 
inch x pitch or 1.08253p 



9-9 



American Standard form of the buttress thread 
has a 7 angle on the pressure flank; other forms 
have , 3 , or 5 . However, the American Stan- 
dard form is most often used, and the formulas 
in this section apply to this form. The buttress 
thread can be designed to either push or pull 
against the internal thread of the mating part into 
which it is screwed. The direction of the thrust 
will determine the way you grind your tool for 
machining the thread. An example of the designa- 
tion symbols for an American Standard Buttress 
thread form is as follows: 

6 - 10 (-N BUTT-2) 

where 6 = basic major diameter of 6.000 
inches 

10 = 10 threads per inch 

(* = internal member to push against 
external member) 

N BUTT = National Buttress Form 
2 = class of fit 

NOTE: A symbol such as "*-(" indicates that 
the internal member is to pull against the external 
member. 

The formulas for the basic dimensions of the 
American Standard Buttress external thread are 
as follows: 



Pitch - 



Width of flat at crest = 0.1631 x pitch 
Root radius = 0.0714 x pitch 
Depth of thread = 0.6627 x pitch 

The classes of fit are: 1 = free, 2 = medium, 
3 = close. The specific dimensions involved 
concern the tolerance of the pitch diameter and 
the major diameter and vary according to the 
nominal or basic size. Consult a handbook for 
specific information on the dimensions for the 
various classes of fit. 



an included angle of 60 and a flat on the crest 
and the root of the thread. Pipe threads can be 
either tapered or straight, depending on the in- 
tended use of the threaded part. A description of 
the two types is given in the following para- 
graphs. 



TAPERED PIPE THREADS 

Tapered pipe threads are used to provide a 
pressure-tight joint when the internal and external 
mating parts are assembled correctly. Depending 
on the closeness of the fit of the mating parts, you 
may need to use a sealing tape or a sealer (pipe 
compound) to prevent leakage at the joint. The 
taper of the threads is 3/4 inch per foot. Machine 
and thread the section of pipe at this angle. The 
hole for the internal threads should be slightly 
larger than the minor diameter of the small end 
of the externally threaded part. 

An example of a pipe thread is shown below. 

NPT 1/4-18 
where NPT = tapered pipe thread 

1/4 inside diameter of the pipe in 
inches 

18 = threads per inch 

Figure 9-15 shows the typical dimensions of 
the most common tapered pipe threads. 



STRAIGHT PIPE THREADS 

Straight pipe threads are similar in form to 
tapered pipe threads except that they are not 
tapered. The same nominal outside diameter and 
thread dimensions apply. Straight pipe threads are 
used for joining components mechanically and are 
not satisfactory for high-pressure applications. 
Sometimes a straight pipe thread is used with a 
tapered pipe thread to form a low-pressure seal 
in a vibration free environment. 



PIPE THREADS 

American National Standard Pipe threads are 



CLASSES OF THREADS 

Classes of fit for threads are determined by 




M 6 F 



ANGLE BETWEEN SIDES OF THREAD IS 60. TAPER OF THREAD, ON 
DIAMETER, IS J INCH PER FOOT. 

THE BASIC THREAD DEPTH IS 0.8 X PITCH OF THREAD AND THE 
CREST AND ROOT ARE TRUNCATED AN AMOUNT EQUAL TO 0.039 X PITCH. 
EXCEPTING 8 THREADS PER INCH WHICH HAVE A BASIC DEPTH OF 0.788 
X PITCH AND ARE TRUNCATED 0.045 X PITCH AT THE CREST AND 0.033 
X PITCH AT THE ROOT. 



PIPE SIZE 


Of) 1 
QO 
E<Z 
UJUj 

5Q=tr 
2xu 

i 1 -"- 


PITCH DIAMETER 


U-uj 

>0 
XH< 
i-IOUJ 

O^O: 

ZU.X 

yfc H 


LENGTH OF 
HAND-TIGHT 
ENGAGEMENT 


IMPERFECT 
THREADS 


*9~. 

xSx 
i_o:< 
az2 
uii---' 
a 


&S 
5| 

f 


3 s 

SuJ 
aj 

oc< 
OS 
z<n 

*S 


.gO 

<IU 

0-1 

*< 
3* 

3w 

*$ 


NOMINAL 
PIPE SIZE 


OUTSIDE 
DIAMETER 


U. -J 

o<o 
_z 

OQ.-UJ 

5e 

H-XI- 
<UJ 


fc- 1 

0<Q 

iS 
g* 

55'- 


A 


B 




F 


E 


c 


D 




K 




G 


H 


1/8 


0.405 


27 


0.36351 


0.37476 


0.2638 


0.180 


0.1285 


0.02963 


0.03704 


0.334 


0.39 


1/4 


0.540 


18 


0.47739 


0.48989 


0.4018 


0.200 


0.1928 


0.04444 


0.05556 


0.433 


0.52 


3/8 


0.675 


18 


0.61201 


0.62701 


0.4078 


0.240 


0.1928 


0.04444 


0.05556 


0.568 


0.65 


1/2 


0.840 


14 


0.75843 


0.77843 


0.5337 


0.320 


0.2478 


0.05714 


0.07143 


0.701 


0.81 


3/4 


1.050 


14 


0.96768 


0.98887 


0.5457 


0.339 


0.2478 


0.05714 


0.07143 


0.911 


0.02 


1 


1.315 


ll'/z 


1.21363 


1.23863 


0.6828 


0.400 


0.3017 


0.06957 


0.08696 


1.144 


1.28 



Figure 9-15. Taper pipe thread dimensions. 



for each particular class. The tolerance (amount 
that a thread may vary from the basic dimension) 
decreases as the class number increases. For 
example, a class 1 thread has more tolerance than 
a class 3 thread. The pitch diameter of the 
thread is the most important thread element in 
controlling the class of fit. The major diameter 
for an external thread and the minor diameter 
or bore size for an internal thread are also 
important, however, since they control the crest 
and root clearances more than the actual fit of 
the thread. A brief description of the different 
classes of fit follows: 

Classes 1A and IB: Class 1A (external 
threads) and class IB (internal) threads are used 
where quick and easy assembly is necessary and 
where a liberal allowance is required to permit 
ready assembly, even with slightly bruised or dirty 
threads. 



Classes 2 A and 2B: Class 2A (external) and 
class 2B (internal) threads are the most commonly 
used threads for general applications including 
production of bolts, screws, nuts and similar 
threaded fasteners. 

Classes 3A and 3B: Class 3A (external) and 
class 3B (internal) threads are used where closeness 
of fit and accuracy of lead and angle of thread 
are important. These threads require consistency 
that is available only through high quality 
production methods combined with a very 
efficient system of gauging and inspection. 

Tables of the basic dimensions and the 
maximum and minimum dimensions for each size 
and class of fit of threads are found in most 
publications and handbooks for machinists. An 
example of the dimensions required to accurately 



9-13 



machine a specific class of fit on a thread is shown 
in Table 9-2. 



MEASURING SCREW THREADS 

Thread measurement is needed to ensure that 
the thread and its mating part will fit properly. 
It is important that you know the various measur- 
ing methods and the calculations that are used to 
determine the dimensions of threads. 

The use of a mating part to estimate and 
check the needed thread is common practice 
when average accuracy is required. The thread 
is simply machined until the thread and the mating 
part will assemble. A snug fit is usually desired 
with very little, if any, play between the 
parts. 

You will sometimes be required to machine 
threads that need a specific class of fit, or you 
may not have the mating part to use as a gauge. 
In these cases, you must measure the thread to 
make sure you get the required fit. 

An explanation of the various methods 
normally available to you is given in the follow- 
ing paragraphs. 



THREAD MICROMETER 

Thread micrometers are used to measure the 
pitch diameter of threads. They are graduated and 
read in the same manner as ordinary micrometers. 
However, the anvil and spindle are ground to the 
shape of a thread, as shown in figure 9-16. Thread 
micrometers come in the same size ranges as 
ordinary micrometers: to 1 inch, 1 to 2 inches, 
and so on. In addition, they are available 
in various pitch ranges. The number of threads 
per inch must be within the pitch range of the 
thread. 



RING AND PLUG GAUGES 

Go and no-go-gauges, such as those shown in 
figure 9-17, are often used to check threaded 
parts. The thread should fit the "go" portion 
of the gauge, but should not screw into or 
onto the "no-go" portion. Ring and plug 
gauges are available for the various sizes and 
classes of fit of thread. They are probably the 
most accurate method of checking threads because 
they envelop the total thread form, and in effect, 
check not only the pitch diameter and the major 
and minor diameters, but also the lead of the 
thread. 



Table 9-2. Classes of Fit and Tolerances for 1/4-20 UNC Thread 



1/4-20 UNIFIED SCREW THREAD (EXTERNAL) 



Designation 


Basic 
Major 
Diameter 


Maximum 
Major 
Diameter 


Minimum 
Major 
Diameter 


Basic 
Pitch 
Diameter 


Maximum 
Pitch 
Diameter 


Minimum 
Pitch 
Diameter 


1/4-20UNC-1A 
1/4-20 UNC-2A 
1/4-20UNC-3A 


0.250 
0.250 
0.250 


0.2489 
0.2489 
0.2500 


0.2367 
0.2408 
0.2419 


0.2175 
0.2175 
0.2175 


0.2164 
0.2164 
0.2175 


0.2108 
0.2127 
0.2147 



1/4-20 UNIFIED SCREW THREAD (INTERNAL) 



Designation 


Basic 
Minor 
Diameter 
(Bore Size) 


Maximum 
Minor 
Diameter 
(Bore Size) 


Minimum 
Minor 
Diameter 
(Bore Size) 


Basic 
Pitch 
Diameter 


Maximum 
Pitch 
Diameter 


Minimum 
Pitch 
Diameter 


1/4-20 UNC- IB 
1/4-20 UNC-2B 
1/4-20 UNC-3B 


0.1876 
0.1876 
0.1887 


0.196 
0.196 
0.196 


0.207 
0.207 
0.2067 


0.2175 
0.2175 
0.2175 


0.2248 
0.2223 
0.2211 


0.2175 
0.2175 
0.2175 



ANVIL 







SPINDLE 



Figure 9-16. Measuring threads with a thread micrometer. 



SPINDLE 





MICROMETER 
SCREW 



DOUBLE END LIMIT PLUG THREAD GAGE 





GO RING GAGE 



NO GO RING GAGE 




ADJUSTABLE THREAD SNAP GAGE 



Figure 9-17. Thread gauges. 



THREE WIRE METHOD 

The pitch diameter of a thread can be 
accurately measured by an ordinary micrometer 
and three wires, as shown in figure 9-18. 




MAJOR 
DIA 



MICROMETER ANVIL 



Figure 9-18. Measuring threads using three wires. 

The wire size you should use to measure the 
pitch diameter depends on the number of threads 
per inch. You will obtain the most accurate results 
when you use the best wire size. The best size is 
not always available, but you will get satisfactory 
results if you use wire diameters within a given 
range. Use a wire size as close as possible to the 
best wire size. To determine the wire sizes, use 
these formulas: 

Best wire size = 0.57735 inch x pitch 
Smallest wire size = 0.56 inch x pitch 
Largest wire size = 0.90 inch x pitch 

For example, the diameter of the best wire for 
measuring a thread that has 10 threads per inch 



9-15 



is 0.0577 inch, but you could use any size between 
0.056 inch and 0.090 inch. 

NOTE: The wires should be fairly hard and 
uniform in diameter. All three wires must be the 
same size. You can use the shanks of drill bits as 
substitutes for the wires. 

Use the following formulas to determine what 
the measurement over the wires should be for a 
given pitch diameter. 

Measurement = pitch diameter - (0.86603 
x pitch) + (3 x wire diameter) 

M = PD - (0.86603 x P) + (3 x W) 

Use the actual size of the wires in the formula, 
not the calculated size. 

Example: What should the measurement be 
over the wires for a 3/4-10 UNC-2A thread? First, 
determine the required pitch diameter for a class 
2A 3/4-10 UNC thread. You can find this 
information in charts in several handbooks for 
machinists. The limits of the pitch diameter for 
this particular thread size and class are between 
0.6832 and 0.6773 inch. Use the maximum size 
(0.6832 inch) for this example. Next, calculate the 
pitch for 10 threads per inch. The formula, "one 
divided by the number of threads per inch" will 

give you pitch = -. For 10 TPI, the pitch is 

0. 100 inch. As previously stated, the best wire size 
for measuring 10 TPI is 0.0577 inch, so assume 
that you have this wire size available. Now make 
the calculation. The data collected so far are: 

Thread - 3/4-10 UNC - 2A 
Pitch diameter (PD) = 0.6832 in. 
Pitch (P) = 0.100 in. 
Wire size (W) = 0.0577 in. 

The standard formula for the measurement 
over the wires was M = PD - (0.86603 x p) 
+ (3 x W). Enter the collected data in the correct 
positions of the formula: 

M = 0.6832 in. - (0.86603 in. x 0.100 in.) 
4- (3 x 0.0577 in.) 

M = 0.6832 in. - 0.086603 in. + 0.1731 in. 
M = 0.769697 in. 



The measurement over the wires should be 
0.769697 in. or when rounded to four decimal 
places, 0.7697 in. 

As mentioned in the beginning of the section 
on classes of threads, the major diameter is a 
factor also considered in each different class of 
fit. The basic or nominal major diameter is seldom 
the size actually machined on the outside diameter 
of the part to be threaded. The actual size is 
smaller than the basic size. In the case of the 
3/4 - 10 UNC - 2A thread, the basic size is 0.750 
in.; however, the size that the outside diameter 
should be machined to is between 0.7482 and 
0.7353 in. 



CUTTING SCREW THREADS 
ON A LATHE 

Screw threads are cut on the on the lathe by 
connecting the headstock spindle of the lathe with 
the lead screw through a series of gears to get a 
positive carriage feed. The lead screw is driven 
at the required speed in relation to the headstock 
spindle speed. You can arrange the gearing 
between the headstock spindle and lead screw so 
that you can cut any desired pitch. For example, 
if the lead screw has 8 threads per inch and you 
arrange the gears so the headstock spindle revolves 
four times while the lead screw revolves once, the 
thread you cut will be four times as fine as the 
thread on the lead screw, or 32 threads per inch. 
With the quick-change gear box, you can quickly 
and easily make the proper gearing arrangement 
by placing the levers as indicated on the index 
plate for the thread desired. 

When you have the lathe set up to control the 
carriage movement for cutting the desired thread 
pitch, your next consideration is shaping the 
thread. Grind the cutting tool to the shape 
required for the form of the thread to be cut, that 
is V-form, Acme, square, and so on. 

MOUNTING WORK IN THE LATHE 

When you mount work between lathe centers 
for cutting screw threads, be sure the lathe dog 
is securely attached before you start to cut the 
thread. If the dog should slip, the thread will be 
ruined. Do not remove the lathe dog from the 
work until you have completed the thread. If you 
must remove the work from the lathe before the 
thread is completed, be sure to replace the lathe 
dog in the same slot of the driving plate. 



9-16 



When you thread work in the lathe chuck, be 
sure the chuck jaws are tight and the work is well 
supported. Never remove the work from the 
chuck until the thread is finished. 

When you thread long slender shafts, use a 
follower rest. You must use the center rest to 
support one end of long work that is to be 
threaded on the inside. 



POSITIONING OF COMPOUND REST 
FOR CUTTING SCREW THREADS 

Ordinarily on threads of fine lead, you feed 
the tool straight into the work in successive cuts. 
For coarse threads, it is better to set the compound 
rest at one-half of the included angle of the thread 
and feed in along the side of the thread. For the 
last -few finishing cuts, you should feed the tool 
straight in with the crossfeed of the lathe to make 
a smooth, even finish on both sides of the thread. 

In cutting V-form threads and when maximum 
production is desired, it is customary to place the 
compound rest of the lathe at an angle of 29 1/2 , 
as shown in Part A of figure 9-19. When you set 
the compound rest in this position and use the 



compound rest screw to adjust the depth of cut, 
you remove most of the metal by using the left 
side of the threading tool (B of fig. 9-19). This 
permits the chip to curl out of the way better than 
if you feed the tool straight in, and keeps the 
thread from tearing. Since the angle on the side 
of the threading tool is 30 , the right side of the 
tool will shave the thread smooth and produce a 
better finish; although it does not remove enough 
metal to interfere with the main chip, which is 
taken by the left side of the tool. 



USING THE THREAD-CUTTING STOP 

Because of the lost motion caused by the play 
necessary for smooth operation of the change 
gears, lead screw, half-nuts, and so forth, you 
must withdraw the thread-cutting tool quickly at 
the end of each cut. If you do not withdraw the 
tool quickly the point of the tool will dig into the 
thread and may break off. 

To reset the tool accurately for each successive 
cut and to regulate the depth of the chip, use the 
thread-cutting stop. 

First, set the point of the tool so that it just 
touches the work, then lock the thread-cutting 
stop by turning the thread-cutting stop screw A 




DIRECTION OF 
FEED 



B 



28.150X 



(fig. 9-20) until the shoulder is tight against stop 
B (fig. 9-20). When you are ready to take the first 
chip, run the tool rest back by turning the 
crossfeed screw to the left several times, and move 
the tool to the point where the thread is to start. 
Then, turn the crossfeed screw to the right until 
the thread-cutting stop screw strikes the thread- 
cutting stop. The tool is now in the original 
position. By turning the compound rest feed screw 
in 0.002 inch or 0.003 inch, you will have the tool 
in a position to take the first cut. 

For each successive cut after returning the 
carriage to its starting point, you can reset the tool 
accurately to its previous position. Turn the 
crossfeed screw to the right until the shoulder of 
screw A strikes stop B. Then, you can regulate 
the depth of the next cut by adjusting the 
compound rest feed screw as it was for the first 
chip. 

For cutting an internal thread, set the 
adjustable thread-cutting stop with the head of 
the adjusting screw on the inside of the stop. 
Withdraw the tool by moving it toward the center 
or axis of the lathe. 

You can use the micrometer collar on the 
crossfeed screw in place of the thread-cutting stop, 
if you desire. To do this, first bring the point of 
the threading tool up so that it just touches the 
work; then adjust the micrometer collar on the 
crossfeed screw to zero. Make all adjustments for 
obtaining the desired depth of cut with the 
compound rest screw. Withdraw the tool at the 
end of each cut by turning the crossfeed screw to 
the right one turn, stopping at zero. You can then 
adjust the compound rest feed screw for any 
desired depth. 



MICROMETER 
COLLAR 




ENGAGING THE THREAD 
FEED MECHANISM 

When cutting threads on a lathe, clamp the 
half-nuts over the lead screw to engage the 
threading feed and release the half nut lever at 
the end of the cut by means of the threading lever. 
Use the threading dial (discussed in chapter 7 and 
illustrated in fig. 7-37) to determine when to 
engage the half-nuts so the cutting tool will follow 
the same path during each cut. When an index 
mark on the threading dial aligns with the witness 
mark on its housing, engage the half-nuts. For 
some thread pitches you can engage the half-nuts 
only when certain index marks are aligned with 
the witness mark. On most lathes you can engage 
the half -nuts as follows: 

For all even-numbered threads per inch, close 
the half -nuts at any line on the dial. 

For all odd-numbered threads per inch, close 
the half-nuts at any numbered line on the dial. 

For all threads involving one-half of a thread 
in each inch, such all 1/2, close the half-nuts 
at any odd-numbered line. 

CUTTING THE THREAD 

After setting up the lathe, as explained 
previously, take a very light trial cut just deep 
enough to scribe a line on the surface of the work, 
as shown in A of figure 9-21 . The purpose of this 
trial cut is to be sure that the lathe is arranged 
for cutting the desired pitch of thread. 

To check the number of threads per inch, 
place a rule against the work, as shown in B of 
figure 9-21, so that the end of the rule rests on 
the point of a thread or on one of the scribed lines. 
Count the scribed lines between the end of the rule 



)-CUTTING 
STOP 





B 



28.151X 

M *-. ji4sxw% MsvM****l j-vwft 



28.152X 



and the first inch mark. This will give the number 
of threads per inch. 

It is quite difficult to accurately count fine 
pitches of screw threads. A screw pitch gauge, 
used as illustrated in figure 9-22, is very 
convenient for checking the finer screw threads. 
The gauge consists of a number of sheet metal 
plates in which are cut the exact forms of threads 
of the various pitches; each plate is stamped with 
a number indicating the number of threads per 
inch for which it is to be used. 

LUBRICANTS FOR CUTTING 
THREADS 

To produce a smooth thread in steel, use lard 
oil as a lubricant. If you do not use oil, the 
cutting tool will tear the steel, and the finish will 
be very rough. 

If lard oil is unavailable, use any good 
cutting oil or machine oil. If you experience 
trouble in producing a smooth thread, add a 
little powdered sulfur to the oil. 




Apply the oil generously before each cut. A 
small paint brush is ideal for applying the oil when 
you cut external screw threads. Since lard oil is 
quite expensive, many machinists place a small 
tray or cup just below the cutting tool on the lathe 
cross slide to catch the surplus oil that drips off 
the work. 

RESETTING THE TOOL OR PICKING 
UP THE EXISTING THREAD 

If the thread-cutting tool needs resharpening 
or gets out of alignment or if you are chasing the 
threads on a previously threaded piece, you must 
reset the tool so it will follow the original thread 
groove. To reset the tool, you may (1) use the 
compound rest feed screw and crossfeed screw to 
jockey the tool to the proper position, (2) 
disengage the change gears and turn the spindle 
until the tool is positioned properly, or (3) loosen 
the lathe dog (if used) and turn the work until the 
tool is in proper position in the thread groove. 
Regardless of which method you use, you will 
usually have to reset the micrometer collars on 
the crossfeed screw and the compound rest screw. 

Before adjusting the tool in the groove, use 
the appropriate thread gauge to set the tool square 
with the workpiece. Then with the tool a few 
thousandths of an inch away from the workpiece, 
start the machine and engage the threading 
mechanism. When the tool has moved to a 
position near the groove into which you plan to 
put the tool, such as that shown by the solid tool 
in figure 9-23, stop the lathe without disengaging 
the thread mechanism. 

To reset the cutting tool into the groove, you 
will probably use the compound rest and crossfeed 
positioning method. By adjusting the compound 
rest slide forward or backward, you can move the 
tool laterally to the axis of the work as well as 
toward or away from the work. When the point 
of the tool coincides with the original thread 




Tiaiir0 QJJ.1 _ 



nifrh 



28.153 28.154X 

Fianre 0.1.1. Tool must hp reset tn nrioinfil ornnvp. 



groove (phantom view of the tool in fig. 9-23), 
use the crossfeed screw to bring the tool point 
directly into the groove. When you get a good fit 
between the cutting tool and the thread groove, 
set the micrometer collar on the crossfeed screw 
on zero and set the micrometer collar on the 
compound rest feed screw to the depth of cut 
previously taken. 

NOTE: Be sure that the thread mechanism is 
engaged and the tool is set square with the work 
before adjusting the position of the tool along the 
axis of the workpiece. 

If it is inconvenient to use the compound rest 
for readjusting the threading tool, loosen the lathe 
dog (if used); turn the work so that the threading 
tool will match the groove, and tighten the lathe 
dog. If possible, however, avoid doing this. 

Another method, which is sometimes used, is 
to disengage the reverse gears or the change gears; 
turn the headstock spindle until the point of the 
threading tool enters the groove in the work, and 
then reengage the gears. 



as the lathe must be run very slowly to obtain 
satisfactory results with the drilled hole. 



LEFT-HAND SCREW THREADS 

A left-hand screw (fig. 9-25) turns counter- 
clockwise when advancing (looking at the head 
of the screw), or just the opposite to a right-hand 
screw. Left-hand threads are used for the 
crossfeed screws of lathes, the left-hand end of 
axles, one end of a turnbuckle, or wherever an 
opposite thread is desired. 

The directions for cutting a left-hand thread 
on a lathe are the same as those for cutting a right- 
hand thread, except that you swivel the compound 
rest to the left instead of to the right. Figure 9-26 
shows the correct position for the compound rest. 
The direction of travel for the tool differs from 
a right-hand thread in that it moves toward the 
tailstock as the thread is being cut. 

Before starting to cut a left-hand thread, it is 
good practice, if feasible, to cut a neck or groove 
into the workpiece. (See fig. 9-25). Such a groove 



FINISHING THE END 
OF A THREADED PIECE 

The end of a thread may be finished by any 
one of several methods. The 45 chamfer on the 
end of a thread, as shown in A of figure 9-24, 
is commonly used for bolts and capscrews. For 
machined parts and special screws, the end is often 
finished by rounding it with a forming tool, as 
shown in B of figure 9-24. 

It is difficult to stop the threading tool 
abruptly, so some provision is usually made for 
clearance at the end of the cut. In A of figure 9-24, 
a hole has been drilled at the end of the thread; 
in B of figure 9-24, a neck or groove has been 
cut around the shaft. The groove is preferable, 




FINISHING END OF THREAD 
WITH 45 CHAMFER 



FINISHING END OF THREAD 
WITH FORM TOOL 



28.155X 
Figure 9-24. Finishing the d of a threaded piece. 




28.156X 



Figure 9-25. A left-hand screw thread. 



DIRECTION OF TOOL TRAVEL 




Figure 9-26. Setup for left-hand external threads. 



enables you to run the tool in for each pass, as 
you do for a right-hand thread. 

Make the final check for both diameter and 
pitch of the thread, whether right-hand or left- 
hand, with the nut that is to be used, or with a 
ring thread gauge if one is available. The nut 
should fit snugly without play or shake but should 
not bind on the thread at any point. 



MULTIPLE SCREW THREADS 

A multiple thread, as shown in figure 9-27, 
is a combination of two or more threads, parallel 
to each other, progressing around the surface 
into which they are cut. If a single thread is 
thought of as taking the form of a helix, that is 
of a string or cord wrapped around a cylinder, 
a multiple thread may be thought of as several 
cords lying side by side and wrapped around a 
cylinder. There may be any number of threads, 
and they start at equally spaced intervals around 
the cylinder. Multiple threads are used when rapid 
movement of the nut or other attached parts is 
desired and when weakening of the thread must 
be avoided. A single thread having the same lead 
as a multiple thread would be very deep compared 
to the multiple thread. The depth of the thread 
is calculated according to the pitch of the thread. 

The tool selected for cutting multiple threads 
has the same shape as that of the thread to be cut 
and is similar to the tool used for cutting a single 
thread except that greater side clearance is 
necessary. The helix angle of the thread increases 
as the number of threads increases. The general 
method for cutting multiple threads is about the 
same as for single screw threads, except that the 
lathe gearing must be based on the lead of the 
thread (number of single threads per inch), and 
not the pitch, as shown in figure 9-27. Provisions 
must also be made to obtain the correct spacing 




of the different thread grooves. You can get the 
proper spacing by using the thread-chasing dial, 
setting the compound rest parallel to the ways, 
using a faceplate, or using the change gear box 
mechanism. 

The use of the thread-chasing dial (fig. 9-28) 
is the most desirable method for cutting 60 multi- 
ple threads. With each setting for depth of cut 
with the compound, you can take successive cuts 
on each of the multiple threads so that you can 
use thread micrometers. 

To determine the possibility of using the 
thread-chasing dial, first find out if the lathe can 
be geared to cut a thread identical to one of the 
multiple threads. For example, if you want to cut 
10 threads per inch, double threaded, divide the 
number of threads per inch (10) by the multiple 
(2) to get the number of single threads per inch 
(5). Then gear the lathe for 5 threads per inch. 

To use the thread-chasing dial on a specific 
machine, refer to instructions usually found 
attached to the lathe apron. To cut 5 threads per 
inch, on most lathes, engage the half -nut at any 
numbered line on the dial, such as points 1 and 
2 shown in figure 9-28. The second groove of a 
double thread lies in the middle of the flat 
surface between the grooves of the first thread. 
Engage the half -nut to begin cutting the second 
thread when an unnumbered line passes the 
index mark, as shown in figure 9-28. To ensure 
that you cut each thread to the same depth, engage 
the half-nut first at one of the numbered positions 
and cut in the first groove. Then engage the half 
nut at an unnumbered position so that alternate 




BEGIN THREAD 
NUMBER 1 



BEGIN THREAD 
NUMBER 2 




FOR FIRST THREAD, SPIIT 
NUT CLOSED AT POINT "l" 



FOR SECOND THREAD, SFLIT 
NUT CLOSED AT POINT ~2* 



SINGLE THREAD DOUBLE THREAD TRIPLE THREAD 




TOOL IN LINE 
FOR FIRST THREAD 



TOOL IN LINE FOR 
SECOND THREAD 



Figure 9-27. Comparison of single and multiple-lead 
threads. 



Figure 9-28. Cutting multiple threads using the thread- 
chasing dial. 



cuts bring both thread grooves down to size 
together. To cut a multiple thread with an even 
number of threads, first use the thread-chasing 
dial to cut the first thread. Then use one of the 
other multiple thread cutting procedures to cut 
the second thread. 

Cutting of multiple threads by positioning the 
compound rest parallel to the ways should be 
limited to square and Acme threads. To use this 
method, set the compound rest parallel to the 
ways of the lathe and cut the first thread to the 
finished size. Then feed the compound rest and 
tool forward, parallel to the thread axis a distance 
equal to the pitch of the thread and cut the next 
thread. 

The faceplate method of cutting multiple 
threads involves changing the position of the work 
between centers for each groove of the multiple 
thread. One method is to cut the first thread 
groove in the conventional manner. Then, remove 
the work from between centers and replace it bet- 
ween centers so the tail of the dog is in another 
slot of the drive plate, as shown in figure 9-29. 
Two slots are necessary for a double thread, three 
slots for a triple thread, and so on. The number 
of multiples you can cut by this method depends 
on the number of equally spaced slots there are 
in the drive plate. There are special drive or 
index plates available, so that you can accurately 
cut a wide range of multiples by this method. 

Another method of cutting multiple threads 
is to disengage either the stud gear or the spindle 
gear from the gear train in the end of the lathe 
after you cut a thread groove. Then turn the work 
and the spindle the required part of a revolution, 
and reengage the gears for cutting the next thread. 
If you are to cut a double thread on a lathe that 
has a 40-tooth gear on the spindle, cut the first 
thread groove in the ordinary manner. Then mark 



one of the teeth on the spindle gear that meshes 
with the next driven gear. Carry the mark onto 
the driven gear, in this case the reversing gear. 
Also mark the tooth diametrically opposite the 
marked spindle gear tooth (the 20th tooth of the 
40-tooth gear). Count the tooth next to the 
marked tooth as tooth number one. Then 
disengage the gears by placing the tumbler 
(reversing) gears in the neutral position, turn the 
spindle one-half revolution or 20 teeth on the 
spindle gear, and reengage the gear train. You 
may index the stud gear as well as the spindle gear. 
If the ratio between the spindle and stud gears is 




B 



28.158X 
Figure 9-30. Cutting thread on tapered work. 




DOG REVOLVED 180 
FOR DOUBLE THREAD 




Figure 9-29. Use of face plate. 



not 1 to 1 , you will have to give the stud gear a 
proportional turn, depending upon the gearing 
ratio. The method of indexing the stud or 
spindle gears is possible only when you can evenly 
divide the number of teeth in the gear indexed by 
the multiple desired. Some lathe machines have 
a sliding sector gear that you can readily insert 
into or remove from the gear train by shifting a 
lever. Graduations on the end of the spindle show 
when to disengage and to reengage the sector gear 
for cutting various multiples. 

THREADS ON TAPERED WORK 

Use the taper attachment when you cut a 
thread on tapered work. If your lathe does not 



have a taper attachment, cut the thread on tapered 
work by setting over the tailstock. The setup is 
the same as for turning tapers. 

Part A of figure 9-30 shows the method 
of setting the threading tool with the thread 
gauge when you use the taper attachment. 
Part B of figure 9-30 shows the same 
operation for using the tailstock setover 
method. 

Note that in both methods illustrated in 
figure 9-30, you set the threading tool square with 
the axis by placing the center gauge on the straight 
part of the work, NOT on the tapered section. 
This is very important. 



CHAPTER 10 

TURRET LATHES AND 
TURRET LATHE OPERATIONS 



Horizontal and vertical turret lathes are 
generally used to produce several identical 
workpieces. Because turret lathes are designed for 
production work, they have many automatic 
features that are not found on engine lathes. For 
greatest efficiency, a turret lathe must be set up 
so the operator can perform the machining steps 
with a minimum amount of control. 

In this chapter we shall discuss turret lathes 
and some of the important factors in the tooling 
setup. 



NEVER completely trust the auto- 
matic stops on a turret lathe. Be alert at all 
times to the progress and movement of the cutting 
tool(s). 

NEVER exceed the recommended depth of 
cut, cutting speeds, and feeds. 

Before starting a vertical turret lathe, 
always be alert for tools, clamping devices, or 
other materials adrift on the lathe table. 



TURRET LATHE SAFETY 

Before learning to operate a turret lathe, you 
must realize the importance of observing safety 
precautions. As in all machine operations, 
you have one guideline: SAFETY FIRST, 
ACCURACY SECOND, AND SPEED LAST. 
The safety precautions listed in chapter 8 for 
engine lathes apply also to turret lathes. Listed 
below are additional safety precautions that you 
must observe to safely operate both horizontal 
and vertical turret lathes. 

Do NOT use a turret lathe that you are not 
authorized and fully qualified to operate. 

@ Wear goggles or a face shield whenever you 
operate a turret lathe. 

Be sure that long stock extending from 
the turret lathe is properly guarded and 
supported. 

Be aware of tools mounted on the 
turret heads. If you are not careful they will 
strike you when the turrets rotate to a new 
station. 



HORIZONTAL TURRET LATHES 

The horizontal turret lathe is a modification 
of the engine lathe. The biggest difference is 
that the turret lathe has two multifaced tool- 
holders. One toolholder (or turret head, as it is 
called) is located where the tailstock is on an 
engine lathe. In a typical turret lathe, the 
turret head has six faces, on each of which 
can be fastened various single tools or groups 
of cutting tools. The other turret toolholder 
(usually square and therefore called the square 
turret) is mounted on a cross slide found on 
an engine lathe. A typical cross slide turret 
can hold one cutting tool on each face. However, 
some types can mount two or more tools on one 
face. Each turret rotates about an upright 
axis. Thus, if you mount the proper cutting 
tools on the turrets, you can do several different 
machining operations in rapid sequence by merely 
rotating another tool or set of tools into position 
for feeding into the work. Moreover, you can do 
simultaneous machining operations. For instance, 
on a particular job, the cross slide turret tool 
may be taking an external cut on the workpiece 
while a tail-mounted tool on the turret head is 
performing an internal machining operation on 
the piece, such as boring, reaming, drilling, or 
tapping. 



10-1 




Figure 10-1. Bar machine. 



CLASSIFICATION OF HORIZONTAL 
TURRET LATHES 

Figures 10-1 and 10-2 show two types of 
horizontal turret lathes, the bar machine and the 
chucking machine. One main difference between 
the two is the size and shape of the work they will 
machine. Bar machines are used for making parts 
out of bar stock or for machining castings or 
forgings of a size and shape similar to bar stock. 
(Note that the bar machine (fig. 10-1) has a stock 
feed attachment.) Chucking machines are used for 



28.159 




A-BAR TURNING SETUP 




28.160 




Figure 10-2. Chucking machine. 



B-CHUCK1NG SETUP 

Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.161X 
Figure 10-3. Hexagonal turret turning tool setups. 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.342X 



Figure 10-4. Ram type bar machine. 



machining castings, forgings, and cut bar stock 
that must be held in a chuck or fixture because 
of their large size or odd shape. The other main 
difference between bar and chucking machines is 
in the types of turning tools and holders used with 
the machines. 

Since the bar machine is designed to machine 
pieces that have a relatively small cross section, 
its hexagonal turret turning tools must be able to 
support the work during cutting; otherwise, the 
workpiece will very likely bend away from the 
cutting tool. 

The stock material which the chucking 
lathe is designed to machine is usually rigid 
enough to withstand heavy cutting forces 
without support. Figure 10-3 illustrates the 
difference between a bar setup and chucking 
setup for a hexagonal turret. 

Bar machines and chucking machines may be 
either the ram type (fig. 10-4) or the saddle type 
(fig. 10-5). On the ram type, the turret head is 



mounted on a ram slide, which you can move 
longitudinally on a saddle that is clamped to the 
bedways of the machine. The ram has both 
hand and power longitudinal feeds. To make 
adjustments, you must manually move the 
saddle, on which the ram is mounted, along the 
bedways. The stroke of the ram is relatively short. 
For this reason, the ram type is not used for 
working material that requires longitudinal 
machining with hexagonal turret-held tools. 

The saddle type lathe has the turret head 
mounted directly on the saddle which, with its 
apron or gear box, moves back and forth on the 
bedways. The length of the longitudinal cut you 
can make with a hexagonal turret-held tool is 
limited only by the length of the bedways. 

Hexagonal turrets found on board ship do not 
normally have cross feed. However, cross feed is 
available on some saddle type lathes. An example 
of a cross-sliding hexagonal turret is shown in 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.343X 



Figure 10-5. Saddle type chucking machine. 



figure 10-5. The small handwheel just to the left 
of the large saddle hand feed wheel controls the 
manual crossfeed. There are levers for engaging 
power feed. The hexagonal turret realigns with 
the spindle axis when the cross slide is returned 
to its starting position. 

Standard toolholders are used to provide cross 
feed for the ram type and the fixed center turret 
saddle type. 



COMPONENTS 

Many of the components of turret lathes 
are similar to those of engine lathes. We 
will discuss only the main components of 
the turret lathe that differ in principle of 
operation from the engine lathe components. 
If you clearly understand the construction 
and functions of an engine lathe, you will have 
little difficulty in learning the construction and 
functions of turret lathes. 



Headstock 

The first important unit of any turret lathe is 
the headstock. Many lathes have a multiple-speed 



motor coupled directly to the spindle. Others 
have all-geared heads, which provide an even 
wider range of spindle or chuck speeds. The all- 
geared heads come in a variety of designs, each 
having a different number of speeds and a dif- 
ferent method of selecting and changing the 
speeds. Some models have a preselector that lets 
you set up the different speeds you will need for 
a job before you begin. On these machines, speed 
changes are made through a minimum number of 
rapid changes without interfering with the timing 
of the operation. 



Feed Train 

The feed train of a turret lathe (fig. 10-6) 
transmits power from the spindle of the machine 
to both the cross slide and the hexagonal 
turret. The feed train consists of a head end 
gear box, a feed shaft, a square turret carriage 
apron or gear box, and a hexagonal turret apron 
or gear box. 

The number of different feeds varies, 
depending upon the size and model of the 
machine. On any machine, first select a range of 
feeds by shifting or changing the gears in the head 



SQUARE TURRET 
APRON (GEAR BOX) 




FEED 


SHAFT 



HEXAGONAL TURRET 
APRON (GEAR BOX) 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.165X 



Figure 10-6. Saddle type turret lathe feed train. 



end gear box. Then shift the levers in the aprons 
to select the desired feed. 

Feed Trips and Stops 

To save time in making a number of duplicate 
parts, many horizontal turret lathes have feed trips 
and positive stops on the cross slide unit and the 
hexagonal turret unit saddle or ram which, when 
set, eliminate the need for measuring each piece. 

A 6-station stop roll (fig. 10-7) in the carriage 
and an adjustable stop rod in the head bracket 
allow for duplicating sizes cut with a longitudinal 
movement of the cross slide carriage. Stop screws 
in the stop roll let you set the cutoff for any 
particular operation, and a master adjusting screw 
in the end of the stop rod lets you make an overall 
setup adjustment without disturbing the individual 
stop screws. The dial clips shown in figure 10-7 
are used as a reference for accurately sizing a piece 
by hand feed after the power crossfeed has been 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.166X 

Figure 10-7. Typical longitudinal feed stop arrangement 
for cross slide. 



knocked off by the crossfeed trips shown in 
figure 10-8. 

Turret stop screws on the ram type machine 
are mounted in a stop roll (fig. 10-9) carried in 
the other end of the turret slide. The screw in the 
lowest position of the stop roll controls the travel 
of the working face of the turret. The stop roll 
is connected to the turret so that when a particular 
face of the turret is positioned for work, its mating 
stop screw is automatically brought into the 
correct position. 

To set the hexagonal turret stops on ram type 
machines: 



1 . Run a cut from the turret to get the desired 
dimensions and length. 

2. Stop the spindle, engage the feed lever, and 
clamp the turret slide. 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.168X 

Figure 10-9. Hexagonal turret feed-stop roll on a ram type 
machine. 



3. Turn the stop screw in until the feed knocks 
off; then continue turning the screw in until it hits 
the dead stop. 

On saddle type machines, the stop roll for the 
hexagonal turret is located under the saddle and 




Photo courtesy of the Warner <& Swasey Company, Solon, Ohio 



between the ways (fig. 10-10). The stop roll does 
not move endwise; it automatically rotates as the 
turret revolves. To set the stops: 

1. Move all the dogs back to the other end of 
the roll, where they will be in a convenient 
position. Selected a turret face and allow the 
master stop to engage the loosened stop dog After 
you take the trial cut, the stop dog will slide ahead 
of the master stop. 

2. After you have taken the proper length of 
cut, stop the spindle, engage the longitudinal feed 
lever and clamp the saddle. Then, adjust the stop 
dog to the nearest locking position with the screw 




Photo courtesy of the Warner & Swsey Company. Solon, Ohio 



Figure lO-lO.-Hexagonal turret feed stops on a saddle type 
machine. 



nearest the master stop. When the end of the dog 
is flush with the edge of a locking groove on the 
stop roll, the locking screw nearest the master stop 
will line up automatically with the next locking 
groove. 5 

3. Screw down the first lock screw, at the 
same time pressing the stop dog toward the head 
end of the machine. 

4. Screw down the second lock screw and then 
adjust the stop screw until it moves the master 
stop back to a point where the feed lever knocks 
off. Then tighten the center screw to bind the stop 
in position. p 

Threading Mechanisms 

There are several different methods for 
producing screw threads on a turret lathe The 
most common method is to use taps and dies 
attached to the hexagon turret. The design and 
proper use of these tools will be covered later in 

J? tn h f{f n A thread chasin S attachment 
(tig. 10-11) allows the machining of screw threads 
on a surface up to about 7 inches long. There are 
two major parts to this attachment. The leader 
is a hollow cylindrical shaft that clamps over the 
feed rod of the turret lathe. You can position it 
anywhere along the feed rod for alignment with 
the surface requiring threads. The follower is a 
halt-nut type arrangement, similar to that on an 
engine lathe. It is bolted to the carriage and 
engaged over the threaded part of the leader 
Disengagement is either manual or automatic 
depending on the model. This attachment can 
normally be installed on existing equipment. An 
attachment that requires factory installation is the 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 



lead screw threading attachment. This attachment 
gives the turret lathe the same threading capability 
as an engine lathe. A lead screw extends the work- 
ing length of the lathe to allow for threading long 
workpieces. A quick-change gear box on the head- 
stock end of the lathe provides for a wide and 
rapid selection of a number of threads per inch. 

TURRET LATHE OPERATIONS 

Aside from additional control levers and 
additional automatic features, the principal 
differences between operating an engine lathe and 
a turret lathe lie in the methods of tooling and 



in the methods of setting up the work. In this 
section we will discuss turret lathe tooling 
principles and methods of doing typical jobs in 
horizontal and vertical turret lathes. 

Proper maintenance is important for efficient 
production on a turret lathe. Specific maintenance 
procedures for a specific turret lathe are given in 
the manufacturer's technical manual. Before 
starting a lathe, ensure that all bearings are 
lubricated and that the machine is clean. Turret 
lathes have pressurized lubrication systems and 
have peepholes at strategic points in the system 
so you can tell at a glance whether oil is being 
circulated to the areas where it is required. 



ADJUSTABLE 
CUTTER HOLDER 



FLANGED TOOL HOLDER 
(LONG) 



SLIDE TOOLS (FLANGED MOUNTING 




REVERSIBLE 
ADJUSTABLE CUTTER HOLDER 



MULTIPLE 
TURNING HEAD 



FLOATING REAMER HOLDER 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

Figure 10-12. Turret lathe chucking tools. 28.345X 



Whenever you clean a lathe, use a cloth or a brush 
to remove chips. DO NOT use compressed air. 
Compressed air is likely to blow foreign matter 
into the precision fitted parts, causing extensive 
damage. 

TOOLING HORIZONTAL 
TURRET LATHES 

As previously mentioned, horizontal turret 
lathes fall into two general classes, the bar 
machines and the chucking machines. The 
principal differences between the two classes are 
in the size and shape of the workpieces they 



handle, the type of workholding device, and the 
type of turning tools used on the hexagonal 
turret. In the following paragraphs which describe 
workholding devices, grinding and setting cutters, 
and various machining procedures, we do not 
specify the class of machine involved, because it 
will usually be obvious; where it is not obvious, 
the information applies to horizontal turret lathes 
in general. The preceding comment also applies 
to the two types of machines, the ram type and 
the saddle type. Examples of some of the 
commonly used tools for a chucking machine are 
shown in figure 10-12 and tools for a bar machine 
in figure 10-13. 



CENTER 
DRILLING TOOL 



FLANGED TOOL 
HOLDER 
I SHORT) 



ADJUSTABLE KNEE 
TOOL 



COMBINATION BAR STOP 
AND STARTING DRILL 



COMBINATION TURNER 
AND END FORMER 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 
Figure 10-13. Turret lathe bar tools. 28.346X 



BLOCKED OFF 
FACE 



INTERNAL 
FACE & FORM 



CUT OFF 



ROUGH TURN 




,-- NECK 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.171X 
Figure 10-14. Square turret tool positions. 



As a good turret lathe operator, your aim 
should be to tool and operate the machine to turn 
out a job as rapidly and as accurately as possible. 
Always keep in mind the following factors: 

Keep the total time for a job at a minimum 
by balancing setup time, work-handling time, 
machine-handling time, and actual cutting time. 

Reduce setup time by using universal 
equipment and by arranging the heavier flanged 
type tools in a logical order. 

Select proper standard equipment. Use 
special equipment only when it is justified by the 
quantity of work to be produced. 

Reduce machine handling time by using the 
right size machine and by taking as many multiple 
cuts as possible. 

Reduce cutting time by the following 
methods: (1) Take two or more cuts at the same 
time from one tool station, (2) take cuts from the 
hexagonal turret and the cross slide at the same 
time, and (3) increase feeds by making the setup 
as rigid as possible by reducing tool overhang and 
using rigid toolholders. 




PLUNGER HEAD FINGER HOLDER JJJJJJ SPINDLE 



HOOD 

C 
L. 



COLLET 





SPRING TYPE PUSHOUT COLLET 

Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.172X 



Never block off stations on the square 
turret (See fig. 10-14). 

Keep the distance that each tool projects 
from the hex turret as equal as possible. This will 
minimize the length of travel required to retract 
each tool for indexing to the next one. 



Holding the Work 

Horizontal turret lathes are generally used for 
turning out duplicate machine parts rapidly in 
quantity. The workholding device must allow you 
to quickly place stock material in the machine. 
Moreover, once you have set the tools, the 
workholding device must be able to position and 
hold each succeeding raw workpiece without your 
having to stop to take measurements or make 
adjustments. (Remember: SAFETY FIRST, 
ACCURACY SECOND, SPEED LAST.) The 
semiautomatic collets, arbors, and chucks 
described in the following sections are able to do 
this. 

COLLETS. The spring-type pushout collet 
shown in figure 10-15 is the most widely used. It 
is made in different sizes for use on bar stock up 
to 2 1/2 inches in diameter. The principle upon 
which it works is as follows: When you engage 
the feed head (fig. 10-15A) to advance the stock, 
you simultaneously loosen the grip of the collet. 
When the end of the bar stock butts against a 
stock stop mounted on one face of the hexagonal 
turret, the plunger (Part A in fig. 10-15B) forces 
the partially split tapered end of collet D into the 
taper of the hood C, causing the collet to grip the 
stock firmly. Your one simple movement 
automatically sets the stock material into position 
for machining. 



There are several variations of the spring-type 
collet, but they all depend on the plunger head 
principle for gripping and releasing the stock, 
differing only in the direction of taper on the 
collet. 

ARBORS. For mounting small, rough 
castings or for mounting workpieces of second 
operations, you will often use quick-acting arbors. 

Figure 10-16 is an expanding bushing-type 
arbor. In this type arbor, as draw bar C is pulled 
back, the split bushing D climbs the taper of the 
arbor body, expanding to grip workpiece A tightly 
along its entire length and at the same time forcing 
the workpiece against stop plate B. This type of 
arbor is suitable for roughing work or first 
operations, where a firm grip for heavy feeds is 
more important than accuracy. 

The expanding plug-type arbor (fig. 10-17) 
centers the workpiece more accurately and is 
usually used for second or finishing operations. 
In this type of arbor, when the taperheaded screw 
is pulled to the left by the action of the draw bar 
C, it expands the outer end of the partially split 
plug D enough to grip the workpiece A internally 
and at the same time forces the workpiece tightly 
against the stop plate B. This type or arbor is used 
for holding workpieces that have been bored or 
reamed to size internally, rough machined to size 
externally, and need only a light finishing cut as 
a final operation. 

CHUCKS. These workholding devices fall into 
three classes: (1) universal chucks of the geared 
scroll, geared screw, or box type that have three 
jaws that move at the same time; (2) independent 
chucks, that have jaws that operate independently; 
and (3) combination chucks, that have jaws that 
may be operated either independently, or as a 
group. 




B A 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 



The 2-jaw chuck is used mostly for holding 
small or irregularly shaped work. The jaw screw 
operates both jaws at the same time. Use an 
adapter to attach chuck jaws of various shapes 
to the master jaws. 

The 3-jaw, geared scroll chuck is used more 
than any other type. With standard jaw equip- 
ment, it holds work of regular shape; but it can 
be adapted to hold irregularly shaped work. 

Figure 10-18 shows a 4-jaw combination chuck 
that has two-piece master-jaw construction and 
an independent jaw screw between sections. The 
bottom or master part of the jaw is moved 
by the scroll, and the top part is moved by the 
independent jaw screw. Chucks of this type are 
used mostly to hold irregularly shaped work or 
when a jaw needs to be offset from a true 
circle. On the combination chuck, you use the 
independent movable jaws to true the work in the 
first chuckings. You can then use the same chuck 
for second operations by using the geared scroll 
to operate the jaws when gripping on a finished 
diameter. Soft metal (such as copper shims) is 
often used with chuck jaws for chucking second 
operation work to prevent marring the finish of 
the workpiece. 

Some machines have a power chuck wrench 
that you use with 3-jaw chucks. This attachment 



lets you open and close the chuck by using a lever 
located on the headstock. There is a control knob 
for adjusting the pressure of the chuck to allow 
for gripping different workpieces. An example of 
such an attachment can be seen on the turret lathe 
in figure 10-5 (indicated by the arrow). 

Grinding and Setting Turret Lathe Tools 

The angles to which a turret lathe tool is 
ground and the position at which it is set can 
change the angle that the cutting edge of the tool 
forms with the work. The angles ground and the 
position set affect the chip flow, the pressure 
exerted on the tool, and the amount of feed and 
depth of cut that can be used. Consequently, 
accurate tool angles and proper tool position are 
essential to production when you use a turret 
lathe. 

GRINDING. Some important points to keep 
in mind when you grind turret lathe tools are 

Some cutters are ground wet; others are 
ground dry. High-speed steel cutters are usually 
ground wet, while Stellite and carbide cutters are 
usually ground dry. When grinding a cutter wet, 
keep it well-flooded to prevent heating; nothing 
will ruin a cutter quicker than a wet grinding that 
is partially dry. On the other hand, if the cutter 




C (UNDERSIDE) 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.175X 



A (TOP) 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.176X 



shuold be ground dry, do not dip the tip in 
coolant. Sudden cooling will cause surface cracks, 
which once started will eventually cause the 
cutter tip to fail. 

When a carbide-tipped cutter requires 
sharpening, use the grinder specified in your shop 
for that purpose. Grinding wheels suitable for 
high-speed steel will ruin carbide cutters. 

When you grind a carbide-tipped cutter, 
always be sure that the pressure of the grinding 
is toward the seat of the carbide tip rather than 
away from it. 

The tool angles of single cutters and multiple 
turning head cutters for the square turret and 
hexagonal turret, respectively, are quite similar 
to those of engine lathe tool bits or turning tools. 
But the cutters themselves are usually much larger 
than those used on an engine lathe because the 
turret lathe is designed to remove large quantities 
of metal rapidly. Bar turner cutters, or box tools 
as they are often called, are ground in a different 
manner. 

Bar turner cutters are usually held in a 
semi vertical position. That is, the cutting edge or 
tool point, which is located near the center of the 
cutter end, points slightly toward the cut and 
toward the center of the work. In this position, 
the pressure of the cut is downward through the 
shank of the cutter. 

Bar turner cutters are ground to form the tool 
point on the end of the cutter, near the centerline, 
somewhat like a chisel point. The bar turner cutter 
in figure 10-19 is in the position it would be held 
in the holder. Normally, in sharpening, you grind 
only angle surface A (the top). You hone angle 




SMALL CHIP 



surfaces B and C to remove burrs which result 
from grinding surface A. After repeated sharpen- 
ings, angle surfaces B and C will become too small 
and you must then grind them. The tool angles 
for a bar turner cutter are the same as those on 
a cross slide mounted cutter, but they appear to 
be vastly different because of the difference in tool 
point location. 

CONTROLLING CHIPS. You can control 
chips in one of two ways: (1) get the right 
combination of back and side rake angles in 
combination with speeds and feeds or (2) grind 
on the back rake face of the cutter a chip breaker 
groove that will curl and break chips into short 
lengths. Method (1) is usually the best way. By 
changing the angle slightly, it is possible to throw 
chips in one direction or the other. If you use 
method (2), start the chip breaker groove just 
behind the cutting edge; be careful not to carry 
it through the point of the cutter. A chip breaker 
groove through the point of the cutter will tend 
to break down the cutting point, produce a poor 
quality of finish, and may produce a double chip 
(fig. 10-20). 

SETTING SINGLE AND MULTIPLE 
TURNING CUTTERS. To retain all of its small 
front clearance angle, a turret lathe cutter must 
be set in its holder so that its active cutting edge 
is on the same plane as the centerline of the work, 
and not above center as tool bits are often set in 
engine lathe operation. Part A of figure 10-21 
shows a cutter in the correct position. This cutter- 
workpiece relation is very important when the 
workpiece diameter is small. Observe in part B 
of figure 10-21 the effect of raising the cutter 



15 ACTUAL 

BACK RAKE 




Figure 10-20. Double chip caused by grinding a chip 
breaker groove too close to the cutting edge. 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.178X 
Figure 10-21. Keep cutters on center. 



above center. A cutter set in the position shown 
has only a fraction of the amount of front 
clearance needed under its cutting lip and has an 
unnecessarily large back rake angle. On the other 
hand, if a cutter is set below center for cutting 
small diameter work, the work is very likely to 
climb the cutter, or at least cause violent chatter. 

Figure 10-22 shows how to set a square turret 
and a "reach over" or rear-tool station cutter on 
center. Notice that the cutter in the "reach over" 
toolpost is inverted; the reason for this is that the 
work surface rolls up from underneath. 

In square turrets, you can raise or lower the 
cutter to the correct position by either shims or 
rockers, depending upon the type of base plate 
(fig. 10-23). 

Another factor to consider in setting a cutter 
is the amount of its overhang from the holder. 
Too much overhang will cause the cutter to 
chatter, and insufficient overhang will cause the 
holding device to foul the work. When possible, 
you should keep the amount of overhang equal 
to or slightly less than twice the thickness of the 
cutter shank. 

Each time you regrind a cutter (other than a 
carbide-tipped type), the height of the tool 
point and the length of the cutter itself are 
reduced; therefore, after each grinding you must 
reposition the cutter in its holder to place the tool 
point on center. If you use a shim-type holder, 
raise the cutter to center by adding a shim of 
appropriate thickness (fig. 10-23B) When using 
a rocker arrangement, you need an entirely 
different approach; elevating the reground tool 
point to center by adjusting the rocker will cause 
the clearance and rake angle to change. The best 
way to maintain the proper angles and yet keep 




SQUARE TURRET 



MEASURE FROM TOP OF TURRET, USING 
CUTTER GRINDING AND SETTING GAGE 




REAR TOOLPOST 

USE A SCALE TO MEASURE THE CORRECT 

POSITION OF THE CUTTER PROM TOP OF 

THE CROSS-SLIDE 





6 



Figure 10-22. Setting square turret and "reach over" 
toolpost cutters on center. 



Figure 10-23. A. Use of rockers. B. Use of shims. 



the tool point on center, when using the rocker 
arrangement, is to decrease the top (back and side) 
rake angles and increase the front clearance angle 
slightly at each grinding. This will allow you to 
account for the change in cutter position caused 
by removal of metal from the tool point. Figure 
10-23A shows how this is done. 

The dimensions of carbide-tipped cutters are 
relatively unaffected by grinding; therefore, the 
cutters seldom require alteration in holder setup 
after they have been reground. The shim-type 
holder provides a stable horizontal base for the 
cutter shank and is best for holding carbide-tipped 
cutters. The cutters can be taken out, reground, 
and placed back in and on center without undue 
manipulation. 

The overhead turning cutters, which are 
mounted on the hexagonal turret, must also be on 
center in relation to the work. The principle in- 
volved in setting these cutters is not different from 
that involved in setting the square turret-mounted 
cutters, though at first it may appear to be differ- 
ent. In order to assure yourself that this is so, look 
at figure 10-21 and turn the book so the cutters 



10-14 



point toward the work from above rather than 
from the side. 

Figure 10-24 shows how to set an overhead 
turning cutter on center by using a scale for 
reference in bringing the shank and tool position 
of the cutter into radial line with the center of the 
turning head, which is in alignment with the center 
of the spindle. 

SETTING BAR TURNER CUTTERS. Bar 

turners are held on the hexagonal turret and 
combine in one unit a cutter holder and a backrest 
that travel with the cutter and support the 
workpiece. The backrest holds the work against 
the cutter so that deep cuts can be taken at heavy 
feeds. 

Backrests on bar turners usually have rollers 
to eliminate wear and to make high-speed opera- 
tion possible. Bar turners that have V-backrests 
are used for turning brass where there is no 
problem of wear and where small chips might get 
under rollers and mar the workpiece. 

The rollers on a ROLLER-TYPE TURNER 
may be either ahead of or behind the cutter. If 
they are behind the cutter, they burnish the 
workpiece. This burnishing is often an important 
factor; it may eliminate the need for polishing or 
grinding operations. When a diameter is turned 
so that it is concentric with a finished diameter, 
the rollers are run ahead of the cutter on 
the previously finished surface. Figure 10-25 
illustrates rollers behind and ahead of a cutter. 

The rollers on a UNIVERSAL TURNER are 
set ahead of or behind the cutter by adjusting the 
movable cutter with the rollers remaining in fixed 



MULTIPLE TURNING HEAD 




position. The universal bar turner is illustrated in 
figure 10-26A. Another type, the single-bar turner 
(fig. 10-26B), has adjustable roller arms; the cut- 
ter is fixed, and the rollers can be moved ahead 
of or behind the cutter. 

Use the following steps in setting up a 
SINGLE BAR TURNER: 

1. Extend the bar stock about 1 1/2 to 2 
inches from the collet. Then with a cutter in the 
square turret on the cross slide, turn the bar to 
0.001 inch under the size desired for a length of 
1/2 to 1 inch. 

2. With the roller jaw swung out of position 
(fig. 10-27 A) and with the cutter set above center 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.182X 
Figure 10-25. Rollers. A. Behind cutter. B. Ahead of cutter. 




Photo courtesy of the Warner & Swasey Company. Solon, Ohio 

28.183X 
Figure 10-26. A. Universal bar turner. B. Single bar turner. 



ROLLERS 




SHINE MARK 




B 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.181X 



Figure 10-27. Rubbing a shine mark to establish a center. 
A. Roll jaws out of position. B. Shine mark on the turned 



and 20 from the perpendicular bisector, adjust 
the cutter slide of the turner against the turned 
portion of the bar stock and rub a shine mark on 
the turned portion, as indicated in figure 10-27B. 

3. Set the cutter at the center of the shine 
mark, clamp the cutter tightly in its slide, turn 
the spindle to move the shine mark away from 
the cutter point, and adjust the slide until the 
cutter is 0.0015 inch from the turned diameter. 
You now have the cutter set. Position the rollers 
endwise and adjust them to size. 

4. Align the rollers with the back of the point 
radius of the cutter, as shown in figure 10-28. 
Adjust the rollers with the clamping screws, and 
then clamp them tightly. The rollers are in proper 
adjustment when LIGHT PRESSURE WILL 
STOP THEM FROM TURNING as the bar stock 
is revolved. 

5 . Push the cutter to cutting position with the 
withdrawal lever and take a trial cut. If you have 
a proper setup, the size of the workpiece will be 
accurate to 0.001 inch. 

BAR TURNING. The following pointers 
will be helpful in bar turning: 

To prevent making marks on the work as 
you bring back the turret, always use the 
withdrawal lever before the return stroke of the 
turret. 

When rollers are set to follow the cutter, 
it is usually true that the heavier the cut the better 
the finish. The heavier the cut the greater is the 
pressure against the rollers, and the greater is the 
burnishing action. 

If you are using light cuts, special rollers 
with a steep taper will sometimes produce a better 
finish. 



FACE OF ROLLER IN 
LINE WITH BACK OF i== 
RADIUS OF CUTTER 




Regardless of the depth of cut, there are 
three factors that you must watch to get a high 
grade finish: (1) the faces of the two rollers must 
be in line, (2) the leading corners of the rollers 
must be perfectly round and exactly equal, and 
(3) end play in the rollers should not exceed 0.003 
inch. 

Selecting Speeds and Feeds 

The general rules for feeds and speeds in 
chapter 8 of this manual for engine lathe opera- 
tion apply also to turret lathes. However, since 
the cutters and the machine itself are designed for 
production work, you can take heavier roughing 
cuts than you ordinarily would with an engine 
lathe. 

Bear in mind that the spindle speed of the 
turret lathe must be governed by the surface speed 
at the point of work of the cutter farthest from 
the rotating axis. That is, if you are going to use 
two cutters on a workpiece with one cutter to turn 
a small diameter and the other to cut a much 
larger diameter, the headstock rpm you select 
must be based on the surface speed at the large 
diameter. Disregard the fact that the cutter at the 
small diameter will be cutting at well below its 
usual rate. 

Using Coolants 

Using coolants makes it possible to run the 
lathe at higher speeds, take heavier cuts, and use 
cutters for longer periods without regrinding, thus 
getting maximum service from the lathe. Coolants 
flush away chips, protect machined parts against 
corrosion, and help give a better finish to the 
work. A coolant also helps to provide greater 
accuracy by keeping the work from overheating 
and becoming distorted. Figure 10-29 shows the 
correct and incorrect ways to apply cutting oil or 
coolant. 

Some coolants and the materials with which 
they are used are listed below: 

CAST IRON Soluble oil 1 to 30 ratio, or 
mineral lard oil, or dry 

ALLOY STEEL Soluble oil 1 to 10 ratio, or 
mineral lard oil 

LOW/MEDIUM CARBON STEEL Soluble 
oil 1 to 20 ratio, or mineral lard oil 



Figure 10-28. Rollers aligned with the cutter. 



BRASSES AND BRONZES Soluble oil 1 to 



INCORRECT 




CORRECT 



Figure 10-29. Correct and incorrect ways to apply coolant. 



STAINLESS STEEL Soluble oil 1 to 5 ratio, 
or mineral lard oil 

ALUMINUM Soluble oil 1 to 25 ratio, or 
dry 

MONEL/NICKEL ALLOYS Soluble oil 1 
to 20 ratio, or a sulfur-based oil 

The selection of the best coolant or cutting 
fluid depends on the cutting tool materials, the 
toughness of the metal being machined and the 
type of operation being performed. Simple turn- 
ing may require a coolant that just keeps the 
temperature down and flushes chips away. A 
mixture of soluble oil that has a low oil ratio will 
do this very efficiently. An operation such as 
threading or heavy turning requires something 
that not only cools but also lubricates. A heavier 
soluble oil mixture or mineral lard oil satisfies 
these requirements. 



BORING 

Two general types of boring cutters are 
used tool bits held in boring bars and solid 
forged boring cutters. Tool bits held in boring bars 
are most common. This combination allows great 
flexibility in sizes and types of work that can be 
done. Solid forged cutters, however, are used to 
bore holes too small to be cut with a boring bar 
and inserted cutter. 

The cutter in a STUB BORING BAR is held 
either at a right angle to the bar or extended 
beyond the end of the bar at an angle. This 
extension of the cutter makes it possible to bore 
up to shoulders and in blind holes. The angular 



cutting bar has the added advantage of an 
adjusting screw behind the cutter. 

When the stub boring bar or forged boring bar 
is used, the overhang should be as short as the 
hole and the setup will permit. You should always 
select the largest possible size of boring bar to give 
the cutter as rigid a mounting as possible. Never 
extend the boring cutter farther than is actually 
necessary. You can use sleeves to increase the 
rigidity of small stub boring bars and to reduce 
the effect of overhang. The increased rigidity helps 
to make the work more accurate and allows for 
heavier feeds. 

The HEXAGON TURRET is ordinarily used 
in making boring cuts, although the boring tools 
can be held on the cross slide. The advantages of 
taking a boring cut from the hexagon turret are: 

1 . You can take turning or facing cuts with 
the cross slide at the same time you take a boring 
cut with the turret. 

2. You can combine boring cutters with 
turning cutters in multiple- or single-turning 
heads. 

3. You can mount various size cutters, 
eliminating the need to adjust the cutter as the 
bore size increases. 

4. When a quantity of like pieces is required, 
you can increase boring feed by using a boring 
bar with two cutters. It is good practice when 
using double cutters to rough bore with a piloted 
boring bar to obtain rigidity for heavy feeds and 
then to finish the hole with a stub boring bar held 
in a slide tool. 

Piloted boring bars require a machine with a 
long stroke the saddle type so the turret can 
be moved far enough to pull the piloted bar from 
the pilot bushing and the work before indexing 
the turret. Usually, when the pilot bushing is 
mounted in the chuck close to the work, the 
effective travel of the turret must be about 2 1 /2 
times the length of the workpiece. 

Grinding Boring Cutters 

Boring cutters are ground in the same manner 
as other types of cutters, with one major 
difference. The clearance angles of boring cutters 
must be greater to prevent rubbing since a boring 
tool cuts on the inside instead of on the outside 
of the work. However, the clearance angle must 
not be too great, or the cutting edge will break 
down because of insufficient support. The exact 
amount of front clearance angle will depend on 



the size of the hole you are boring. The smaller 
the hole, the more clearance required. There are 
no set rules for exact clearance angles; knowledge 
of what will be the best angle comes with 
experience. 

Figure 10-30 shows how to center a vertical 
slide tool-held boring cutter. 

Forming 

One of the fastest methods of producing a 
finished diameter or shape is by using a cutter with 
a cutting edge that matches the shape to be 
machined. This procedure is known as forming. 
In planning a setup, you should study the work 
to determine if forming tools can be used. It is 
possible, on many jobs, to combine two or more 
cuts into one operation by using a specially 
designed forming cutter. Forming cutters are also 
used to produce irregular and curved shapes that 
are difficult to produce in any other way. There 
are three types of forming cutters you will use- 
forged, dovetail, and circular. 

FORGED FORMING CUTTERS are made 
in the shop from forged blanks and ordinarily are 
mounted directly in the square turret or toolpost. 
These cutters are the least expensive to make. 
They have, however, the shortest production life. 

DOVETAIL FORMING CUTTERS are 
cutters that may be either bought or made. They 



VERTICAL SLIDE TOOL 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.187X 
Figure 10-30. Setting a boring cutter on center. 



are attached by dovetails to toolholders mounted 
on the cross slide. Their shape or contour is 
machined and ground the full length of the face, 
and the cutters are set in the holder at an angle 
to provide front clearance. When the cutter wears, 
you need to regrind only the top. Dovetail 
cutters cost more than forged cutters, but they 
have a longer production life, are more easily set 
up, maintain their form after grinding, are more 
rigid, and can be operated under heavier feeds. 

CIRCULAR FORMING CUTTERS (fig. 
10-31) have an even longer life than dovetail 
cutters. The shape of circular cutters is ground 
on the entire circumference and, as the cutting 
edge wears away, you regrind only the top. After 
grinding a new cutting edge, move the cutter to 
a new cutting position by rotating the cutter about 
its axis. 

NEVER regrind circular forming cutters on 
a bench grinder. Regrind them on a toolroom 
grinder where they can be rigidly supported and 
ground to maintain the original relief angles. 

Threading 

For turret lathe operations, dies and taps 
provide a way to cut threads easily and quickly 
and, usually, in only one pass over the work. Dies 
and taps for turret lathes are divided into 
three general types: Solid, solid adjustable, and 
collapsing or self-opening. 

Solid taps and dies are usually held in a 
positive drive holder that has an automatic release 
(fig. 10-12). A longitudinal floating action (not 
to be confused with a floating die holder) allows 



CUTTER 



<t OF 
SPINDLE 



HOLDERS USED ON 
FRONT AND REAR 
OF CROSS-SLIDE Bf 
TURNING ECCENTRC 
BUSHING ,180 




FRONT 



REAR 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.188X 
Figure 10-31. Circular forming cutter diagram. 



the tap or die to follow the natural lead of the 
thread. Solid dies are used only when the thread 
to be cut is too coarse for the self-opening die head 
or a solid adjustable die head, or when the tool 
interferes with the setup. 

Solid adjustable taps and dies should be used 
in place of collapsing taps and self-opening die 
heads only when lathe speed is low and when time 
required for a backing out is not important. 

Collapsing taps (fig. 10-32) are used for 
internal threading. They are time-savers because 
you do not have to reverse the spindle to withdraw 
the tap. The pull-off trip type, which is collapsed 
by simply stopping the feed, is the most frequently 
used. 

Various types of self-opening die heads are 
used. One type is shown in figure 10-33. Some 
have flanged backs for bolting directly to the 
turret face; others have shanks which fit into a 
holder. The die heads are fitted with several 
different types of chasers. The tangential and 
circular type chasers can be ground repeatedly 
without destroying the thread shape. They are a 
bit more difficult to set, but they are better 
adapted than flat chasers for long runs of 
identical threads. 

Die heads come with either a longitudinal float 
or a rigid mounting. The floating type die head 
should be used for heavy duty turret lathe work, 
for fine pitch threading, and for finishing rough- 
cut threads. 





Figure 10-33. Pull-off trip self-opening die head. 



On some types of work it is necessary to take 
both roughing and finishing cuts. They are 
normally taken when threading a tough material 
or when a smooth finish is required. Some types 
of die heads have both roughing and finishing 
attachments. If such die heads are not available, 
roughing and finishing cuts can be taken with 
separate dies or taps set up on different turret 
stations. 

As mentioned earlier in this chapter, some 
horizontal turret lathes can cut or chase threads 
with a single-point tool. In such machines, there 
are two methods of feeding the threading tool into 
the work. The first method is to get an angular 
feed to the cutter by means of the compound 
cross-slide (fig. 10-34) or by using the angular 




Figure 10-32. Universal collapsing tap. 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.189X 

Figure 10-34. Compound cross-slide angular feed-in for 
thread cutting. 



threading toolholder (fig. 10-35). By the first 
method, the cutter is fed into the work at an 
angle until the final polishing passes are 
made. For the final polishing passes, the 
cutter is fed straight in by means of the 
cross-slide. The second method is to feed 
the cutter straight into the work for each 
pass, as indicated in figure 10-36. With this 
latter method you apply by hand a slight 
drag to the carriage or saddle during the 
roughing cut and remove the drag during 
the final polishing passes. It takes more 
skill to use the second method, but it produces 
better threads. 



2. The finish must meet requirements. 

3. The taper angle must be accurate. 

It is best to use the roller rest taper turner for 
long taper bar jobs. You can quickly set this tool 
for size by using the graduated dial and then can 
control the angle of taper accurately by using the 
taper guide bar. 

Taper attachments are provided for the cross 
slide of most turret lathes, both ram and saddle 
type. These attachments can be quickly set to 
produce either internal or external tapers. They 



Taper Turning 

Tapers may be produced on a turret lathe with 
(1) forming cutters, (2) roller rest taper turners, 
or (3) taper attachments. 

Forming cutters of the forged, circular, or 
straight dovetail types may be used to produce 
tapers when the workpiece is rigid enough or can 
be supported in such a way that it will with- 
stand the heavy forming cut. If work cannot 
be formed, other methods (described later) must 
be used. 

Work should be shaped with forming cutters 
only under the following conditions: 

1. The work is either self-supporting or is 
supported by a center rest so that chatter is 
prevented. 





Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.191X 
Figure 10-36. Straight-in feeding method of threading. 



;?. BACKLASH 
J3-V ELIMINATOR 



8 7 




1. GUIDE PLATE 

2. BASE PLATE 

3. CARRIAGE PLATE 

4. EXTENSION ROD 



5. SETSCREW 

6. BINDER SCREW 

7. STOP COLLAR 

8. LATCH 



Photo courtesy of the Warner A Swasey Company, Solon, Ohio 

28.190X 

Figure 10-35. Angular feed-in with adjustable threading 
toolholder. 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 

28.192X 

Figure 10-37. Detail of a cross-slide taper attachment for 
a saddle-type machine. 



do not interfere with normal operation when 
not in use. Most taper attachments are movable 
and can be quickly placed at any position on the 
bed. 

Taper attachments all have a pivoting guide 
plate which can be adjusted to any taper angle. 
Figure 10-37 shows a saddle-type taper attachment 
in detail. 

The guide plate (1) pivots on the base plate 
(2), which slides into carriage plate (3). When you 
plan to use the attachment, clamp the extension 
rod (4) to the machine with the setscrew (5), 
and loosen the binder screw (6). You can use the 
stop collar (7) and the latch (8) for locating the 
cross slide unit on the bed of the machine. To use 
the stop collar and the latch, move the cross slide 
unit to the left until the stop collar comes in 
contact with the latch. This locates the entire unit. 

Taper attachments are fitted with a backlash 
eliminator nut (fig 10-37) for the slide screws. 
Tightening this nut against the feed screw removes 
all play between the feed screw and the nut. 

To duplicate accurate sizes when you use a 
taper attachment with other tools in a setup, 



remember these three things; (1) you must locate 
the attachment in the same position in relation 
to the cross slide each time you use it, (2) you 
must locate the cross slide in exactly the same 
spot on the bed when you clamp the extension 
rod with the setscrew, tighten the binder screw, 
and loosen the extension rod, and (3) be sure 
the cross slide is in exactly the same position 
as in (1) above. 

You can produce either internal or external 
threads with the taper attachment in conjunction 
with a lead screw thread chasing attachment. (See 
fig. 10-38). Notice, however, that taper cutting 
with hexagonal turret held cutters is possible 
only on lathes that have a cross-sliding hexagonal 
turret. 



HORIZONTAL TURRET 
LATHE TYPE WORK 

Regardless of the job, your aim as a good 
turret lathe operator is to tool up the machine and 
operate it so the job can be turned out as rapidly 
and as accurately as possible. The following 
examples show you how. 



EXTERNAL TAPER THREAD 



SQUARE TURRET ADJ. 
THD'G TOOLHOLDER 




INTERNAL TAPER THREAD 



TAPER 
ATTACHMENT 



LEADER AND 

FOLLOWER 

OR LEAD SCREW 



TAPER ATTACHMENT 



THREADING TOOL: 
HOLDER 




LEAD SCREW 

OR 
LEADER AND FOLLOWER 



Photo courtesy of the Warner & Swasey Company, Solon, Ohio 



A Shoulder Stud Job 

A shoulder stud, shown in part A of figure 
10-39, is a typical bar job (universal bar equip- 
ment is used) for a small ram-type turret lathe that 
has a screw feed cross slide. The tooling setup for 
the shoulder stud is shown in part B of figure 
10-39. The diameter (5), which must be held to 
a clearance of 0.001-inch tolerance, is formed with 
a cutter on the front of the cross slide. Diameters 
(2) and (3) are turned from the hexagon turret with 
cutters held in the multiple cutter turner. After 
this operation, the radius on the end of the 
workpiece is machined in a combination end facer 
and turner, then the thread is cut, and the piece 
is cut off. 

A Tapered Stud Job 

A tapered stud, shown in part B of figure 
10-40, does not offer much opportunity for taking 
multiple cuts. However, cuts from the cross slide 
can be combined with cuts taken by the hexagon 
turret. The tooling setup for the taper stud, shown 
in part A of figure 10-40, is used for small lot 
production. The almost identical tooling layout 



in part C of figure 10-40 shows the setup for 
medium quantity production. 

In both small and medium lot production, the 
turning of diameter (6) and the forming of 
diameter (7) can be combined with the turning 
of diameter (3). In addition, the facing and 
chamfering of the end (2) can be combined with 
the turning of diameter (7). 

For small lot production (part A of fig. 10-40) 
the taper is generally formed with a standard wide 
cutter, ground to the proper angle. These cuts will 
not be very accurate, but as the taper will be 
ground in a later operation, the job will be 
satisfactory if sufficient stock is left for grinding. 
If a forming tool wide enough to cut the taper 
in one cut is available, it should be used. 

For medium lot production (part C of fig. 
10-40) the cross slide taper attachment may be set 
up and used for single point turning of the taper. 
The same amount of time will probably be 
required to turn the taper (part C, fig. 10-40) as 
to form the taper (part A, fig 10-40). However, 
the turned taper will be more accurate and require 
less stock for grinding. In addition, the grinding 
operation will take less time. 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 



vm^ *' , A */ . / > 





- 



rP 



/0 -' 



v 

TAPKR 




courtesy of the Warner & Swasey Company, Solon, Ohio 



126. HX 

Figure 10-40. A. Tooling setup for a taper stud small lot production. B. A taper stud. C. Tooling setup for a taper stud- 
medium lot production. 



Figure 10-41 shows a simple setup for the 
second operation of the taper stud. The setup is 
the same for producing either a small or a medium 
size quantity. 



VERTICAL TURRET LATHES 

A vertical turret lathe works much like an 
engine lathe turned up on end. You can perform 
practically all of the typical lathe operations in 
a vertical turret lathe, including turning, facing, 
boring, machining tapers, and cutting internal and 
external threads. 

The characteristic features of this machine are: 
(1) a horizontal table or faceplate that holds the 
work and rotates about a vertical axis; (2) a side 
head that can be fed either horizontally or 
vertically; and (3) a turret slide, mounted on a 
crossrail that can feed nonrotating tools either 
vertically or horizontally. 

Figures 10-42 and 10-43 show vertical turret 
lathes similar to those generally found in repair 
ships and tenders. The main advantage of the 
vertical turret lathe over the engine lathe is that 
heavy or awkward parts are easier to set up on 
the vertical turret lathe and, generally, the 
vertical turret lathe will handle much larger 
workpieces than the engine lathe. The size of the 
vertical turret lathe is designated by the diameter 
of the table. For instance, a 30-inch lathe has a 
table 30 inches in diameter. The capacity of a 




(1 ) Main turret head 

(2) Turret slide 

(3) Swivel plate 

(4) Saddle 

(5) Main rails 

(6) Upright bedways 

(7) Side turret 

(8) Side head 

28.170X 
Figure 10-42. A 30-inch vertical turret lathe. 



1 CHUCK 
V BEHOVE 




Photo courtesy of the Warner & Swasey Company, Solon, Ohio 




28.349X 



Figure 10-43. A 36-inch vertical turret lathe. 



specific lathe is related to but not necessarily 
limited to the size of the table. A 30-inch vertical 
lathe (fig. 10-42) can hold and machine (using 
both the main and the side turrets) a workpiece 
up to 34 inches in diameter. If only the main 



turret is used, the workpiece can be as large as 
44 inches in diameter. 

The main difference between the vertical 
turret lathe and the horizontal turret lathe is in 
the design and operating features of the main 



10-25 



IU.1..LVI J.1VC4.U.. 4.WJ.VJ. \,\J 



turret slide (2) is mounted on a swivel plate (3) 
which is attached to the saddle (4). The swivel 
plate allows the turret slide to be swung up to 45 
to the right or left of the vertical, depending on 
the machine model. The saddle is carried on, and 
can traverse, the main rails (5). The main rails are 
gibbed and geared to the upright bedways (6) for 
vertical movement. This arrangement allows you 
to feed main turret tools either vertically or 
horizontally, as compared to one direction on the 
horizontal turret lathe. Also, you can cut tapers 
by setting the turret slide at a suitable angle. 

The side turret and side head of the vertical 
turret lathe correspond to the square turret and 
cross slide of the horizontal turret lathe. A typical 
vertical turret lathe has a system of feed trips 
and stops that function similarly to those on a 
horizontal turret lathe. In addition, the machine 
has feed disengagement devices to prevent the 
heads from going beyond safe maximum limits 
and bumping into each other. 

Vertical turret lathes have varying degrees of 
capabilities, including feed and speed ranges, 
angular turning limits, and special features such 
as threading. 

You can expect to find a more coarse 
minimum feed on the earlier models of vertical 
turret lathes. Some models have a minimum of 
0.008 inch per revolution of the table or chuck, 
while other models will go as low as 0.001 inch 
per revolution. The maximum feeds obtainable 
vary considerably also; however, this is usually 
less of a limiting factor in job setup and 
completion. 

The speeds available on any given vertical 
turret lathe tend to be much slower than those 
available on a horizontal lathe. This reduction of 
speed is often required due to the large and 
oddly shaped sizes of work done on vertical turret 
lathes in Navy machine shops. A high speed could 
cause a workpiece to be thrown out of the 
machine, causing considerable equipment damage 
and possible injury to the machine operator or 
bystanders. 

One of the major differences in operator 
controls between the vertical turret lathes shown 
in figures 10-42 and 10-43 is in the method used 
to position the cutter to the work. The lathe 
in figure 10-42 has a handwheel for manually 
positioning the work. The lathe in figure 10-43 
uses an electric drive controlled by a lever. When 
the feed control lever is moved to the creep 
position, the turret head moves in the direction 
selected in increments as low as 0.0001 inch per 



revolution and can be made with the table 
stopped. 

An attachment available on some machines 
permits threading of up to 32 threads per inch 
with a single point tool. The gears, as specified 
by the lathe manufacturer, are positioned in the 
attachment to provide a given ratio between the 
revolutions per minute of the table and the rate 
of advance of the tool. 

The same attachment also lets the operator 
turn or bore an angle of 1 to 45 in any quadrant 
by positioning certain gears in the gear train. The 
angle is then cut by engaging the correct feed lever. 

Details for turning tapers on a vertical turret 
lathe without this attachment are given later in 
this chapter. 

TOOLING VERTICAL 
TURRET LATHES 

The principles involved in the operation of a 
vertical turret lathe are not very different from 
those just described for the horizontal turret lathe. 
The only significant difference, aside from the 
machine being vertical, is in the main turret. As 
previously mentioned, you can feed the main 
head, which corresponds to the hexagonal turret 
of the horizontal machine, vertically toward the 
headstock (down); horizontally; or at an angle, 
either by engaging both the horizontal and 
vertical feeds or by setting the turret slide at an 
angle from the vertical and using the vertical feed 
only. 

The tool angles for the cutters of the vertical 
machine correspond to those used on cutters in 
the horizontal turret lathe and are an important 
factor in successful cutting. Also, the same 
importance is attached to setting cutters on center 
and maintaining the clearance and rake angles in 
the process. Again, we cannot overemphasize the 
importance of holding the cutters rigidly. 

In vertical turret lathe work, you must often 
use offset or bent-shank cutters, special sweep 
tools, and forming tools, particularly when you 
machine odd-shaped pieces. Many such cutting 
tools are designed to take advantage of the great 
flexibility of operation provided in the main head. 

In a repair ship, the vertical turret lathe is 
normally used for jobs other than straight 
production work. For example, a large valve can 
be mounted on the horizontal face of its worktable 
or chuck much more conveniently than in almost 
any other type of machine used to handle large 
work. Figure 10-44 shows a typical valve seat 



10-26 





Figure 10-44. Refacing a valve seat in a vertical turret lathe. 



refacing job in progress in a vertical turret lathe. 
Figure 10-45 shows the double tooling principle 
applied to a machining operation. 

The tooling principles and the advantage of 
using coolants for cutting as previously described 
for horizontal turret lathes apply equally to 
vertical machines. 



TAPER TURNING ON A 
VERTICAL TURRET LATHE 

The following information regarding taper 
turning on a vertical lathe is based on a Bullard 
vertical turret lathe. (See fig. 10-42.) 

There are several ways to cut a taper on a ver- 
tical turret lathe. You can cut a 45 taper with 
either a main turret-held cutter or a side head-held 
cutter by engaging the vertical and horizontal 
feeds simultaneously. To cut a taper of less than 
30 with a main turret-held tool, set the turret slide 
for the correct degree of taper and use only 
the vertical feed for the slide. The operation 
corresponds to cutting a taper by using the 
compound rest on an engine lathe; the only 
difference is that you use the vertical power feed 
instead of advancing the cutter by manual feed. 

By swiveling the main turret head, you can cut 
30 to 60 angles on the vertical turret lathe 
without having to use special attachments. To 
machine angles greater than 30 and less than 60 
from the vertical, engage both the horizontal feed 



Figure 10-45. Double tooling. 



and the vertical feed simultaneously and swivel the 
head. Determine the angle to which you swivel the 
head in the following manner. For angles between 
30 and 45, swivel the head in the direction 
opposite to the taper angle being turned, as 
illustrated in figure 10-46. The formula for 




Figure 10-46. Head setting for 30 to 45 angles. 



10-27 



determining the proper angle is A = 90 - 2B . 
A sample problem from figure 10-46 follows: 

Formula A 4- 90 ~ 2B 

Example B = 35 

Therefore A = 90 - (2 x 35 ) 

A = 90 - 70 
ANGLE A =20 

For angles between 46 and 60, swivel 
the head in the same direction as the taper 
angle being turned. (See fig. 10-47.) The 
formula for determining the proper angle is 
ANGLE A = 2B - 90. A sample problem 
from figure 10-47 follows: 

Formula A = 2B - 90 

Example B = 56 

Therefore A = (2 x 56) - 90 

A= 112 - 90 
ANGLE A = 22 

Whenever you turn a taper by using the main 
turret slide swiveling method, use great care to 
set the slide in a true vertical position after you 
complete the taper work and before you use the 
main head for straight cuts. A very small 
departure of the slide from the true vertical will 
produce a relatively large taper on straight work. 




Figure 10-47. Head setting for 45 to 60 angles. 



Unless you are alert to this, you may inadvertently 
cut a dimension undersize before you are aware 
of the error. 

Still another way to cut tapers with either a 
main head-held or side head-held tool is to use 
a sweep-type cutter ground and set to the desired 
angle. Then feed it straight to the work to 
produce the desired tapered shape. This, of 
course, is feasible only for short taper cuts. 



10-28 



MILLING MACHINES 
AND MILLING OPERATIONS 



The milling machine removes metal with a 
revolving cutting tool called a milling cutter. With 
various attachments, milling machines can be used 
for boring, slotting, circular milling, dividing, and 
drilling; cutting keyways, racks, and gears; and 
fluting taps and reamers. 

Bed-type and knee and column type milling 
machines are generally found in most Navy 
machine shops. The bed-type milling machine has 
a vertically adjustable spindle. The horizontal 
boring mill discussed later in this chapter is 
a typical bed-type mill. The knee and column 
milling machine has a fixed spindle and a vertically 
adjustable table. There are several classes of 



OVERARM- 



INNER ARBOR 
SUPPORT 

OUTER 1 \ 
ARBOR f 
SUPPORT-\II 



TAILSTOCK- 
TABLE- 



ARBOR SPINDLE NOSE 
COLUMN 



f 



DIVIDING 
.HEAD 

ENCLOSED 
DIVIDING HEAD 

LEAD DRIVE 
[MECHANISM 












ELEVATION SCREWI 



28.362X 



Figure 11-1. Universal milling machine. 



milling machines within these types but only the 
classes with which you will be concerned are 
discussed in this chapter. 

You must be able to set up the milling machine 
to machine flat, angular, and formed surfaces. 
Included in these jobs are the milling of keyways, 
hexagonal and square heads on nuts and bolts, 
T-slots and dovetails, and spur gear teeth. To set 
up a milling machine, you must compute feeds 
and speeds, select and mount the proper holding 
device, and select and mount the proper cutter to 
handle the job. 

Like other machines in the shop, milling 
machines have manual and power feed systems, 
a selective spindle speed range, and a coolant 
system. 



KNEE AND COLUMN 
MILLING MACHINES 

The Navy uses three types of knee and column 
milling machines; the universal type, the plain 
type, and the vertical spindle type. Wherever only 
one type of machine can be installed, the universal 
type is usually selected. 

The UNIVERSAL MILLING MACHINE 
(fig. 11-1) has all the principal features of the 
other types of milling machines. It can handle 
practically all classes of milling work. You can 
take vertical cuts by feeding the table up or down. 
You can move the table in two directions in the 
horizontal plane either at a right angle to the axis 
of the spindle or parallel to the axis of the spin- 
dle. The principal advantage of the universal mill 
over the plain mill is that you can swivel the table 
on the saddle. Thus, you can move the table in 
the horizontal plane at an angle to the axis of the 
spindle. This machine is used to cut most types 
of gears, milling cutters, and twist drills, and is 
used for various kinds of straight and taper work. 



11-1 



TILT LOCK 
SCREWS 





CROSS SLIDE 



Figure ll-2.-Plain Milling Machine. 



2S.365X 



v . ., 2S.364X 

Figure ll-4.-Small vertical milling machine. 



STARTING LEVER < 
VERTICAL HEAD CLAMP. X 



ARBOR-LOCK 
SPINDLE NOSE 



SPEED CHANGE 
DIAL 



SPEED 
CALCULATOR 



SPINDLE 

REVERSE 

LEVER 



TABLE 

TRAVERSE am 
HANDWHEEL 



AUTOMATIC 
LUBRICATION 



KNEE 
CLAMP 



REAR TABLE FEED 
ENGAGING LEVER 



FOUR POSITION 
TURRET STOP 



POWER FEED ENGAGING 
FOR VERTICAL HEAD 



VERTICAL HEAD 
HANDWHEEL 



AUTOMATIC BACKLASH 
ELIMINATOR KNOB 




TELESCOPIC 
COOLANT RETURN 



OIL FILTER 



Figure 11-3. Vertical spindle milling machine. 



28.363X 



a lew 01 me icaiures lounu on me otner macmnes. 
You can move the table in three directions: 
longitudinally (at a right angle to the spindle), 
transversely (parallel to the spindle), and vertically 
(up and down). The ability of this machine to 
take heavy cuts at fast speeds is its chief 
value and is made possible by the machine's rigid 
construction. 

The VERTICAL SPINDLE MILLING 
MACHINE (fig. 1 1-3) has the spindle in a vertical 
position and at a right angle to the surface of the 
table. The spindle has a vertical movement, and 
the table can be moved vertically, longitudinally, 
and transversely. Movement of both the spindle 
and the table can be controlled manually or by 
power. The vertical-spindle milling machine can 
be used for face milling, profiling, die sinking, 



various smaii vertical spincue mining macnmes 
(fig. 11 -4) are also available for light, precision 
milling operations. 



MAJOR COMPONENTS 

You must know the name and purpose of each 
of the main parts of a milling machine to under- 
stand the operations discussed later in this 
chapter. Keep in mind that although we are 
discussing a knee and a column milling machine 
you can apply most of the information to the 
other types. 

Figure 11-5, which illustrates a plain knee and 
column milling machine, and figure 11-6, which 
illustrates a universal knee and column milling 



SPINDLE 
STARTING LEVER 




REAR POWER TABLE 
FEED LEVER 



SPINDLE SPEED 
SELECTOR DIAL 



POWER VERTICAL 
FEED LEVER 



28.365X 



Figure 11-5. Plain milling machine, showing operation controls. 

11-3 




o 



N 



A. SPINDLE 

B. ARBOR SUPPORT 

C. SPINDLE CLUTCH LEVER 

D. SWITCH 

E. OVERARM 

F. COLUMN 



G. SPINDLE SPEED SELECTOR LEVERS 
H. SADDLE AND SWIVEL 
I. LONGITUDINAL HANDCRANK 
J. BASE 
K. KNEE 
L. FEED DIAL 



M. KNEE ELEVATING CRANK 
N. TRANSVERSE HANDWHEEL 
O. VERTICAL FEED CONTROL 
P. TRANSVERSE FEED LEVER 
Q. TABLE FEED TRIP DOG 
R. LONGITUDINAL FEED CONTROL 



Figure 11-6. Universal knee and column milling machine with horizontal spindle. 



28.366 



11-4 



machine, will help you to become familiar with 
the location of the parts. 

COLUMN: The column, including the base, 
is the main casting which supports all the other 
parts of the machine. An oil reservoir and a pump 
in the column keep the spindle lubricated. The 
column rests on a base that contains a coolant 
reservoir and a pump that you can use when you 
perform any machining operation that requires 
a coolant. 

KNEE: The knee is the casting that supports 
the table and the saddle. The feed change gear- 
ing is enclosed within the knee. It is supported 
and can be adjusted by turning the elevating 
screw. The knee is fastened to the column by 
dovetail ways. You can raise or lower the knee 
by either hand or power feed. You usually use 
hand feed to take the depth of cut or to position 
the work and power feed to move the work during 
the machining operation. 

SADDLE and SWIVEL TABLE: The saddle 
slides on a horizontal dovetail (which is parallel 
to the axis of the spindle) on the knee. The swivel 
table (on universal machines only) is attached to 
the saddle and can be swiveled approximately 45 
in either direction. 

POWER FEED MECHANISM: The power 
feed mechanism is contained in the knee and 
controls the longitudinal, transverse (in and out) 
and vertical feeds. You can obtain the desired rate 
of feed on machines, such as the one shown in 
figure 1 1-5, by positioning the feed selection levers 
as indicated on the feed selection plate. On 
machines such as the one in figure 11-6, you get 
the feed you want by turning the speed selection 
handle until the desired rate of feed is indicated 
on the feed dial. Most milling machines have a 



rapid traverse lever that you can engage when you 
want to temporarily increase the speed of the 
longitudinal, transverse, or vertical feeds. For 
example, you would engage this lever to position 
or align the work. 

NOTE: For safety reasons, you must exercise 
extreme caution whenever you use the rapid 
traverse controls. 

TABLE: The table is the rectangular casting 
located on top of the saddle. It contains several 
T-slots for fastening work or workholding devices 
to it. You can move the table by hand or by 
power. To move the table by hand, engage and 
turn the longitudinal handcrank. To move it by 
power, engage the longitudinal directional feed 
control lever. You can position the longitudinal 
directional feed control lever to the left, to 
the right, or in the center. Place the end of the 
directional feed control lever to the left to feed 
the table toward the left. Place it to the right to 
feed the table toward the right. Place it in the 
center position to disengage the power feed or to 
feed the table by hand. 

SPINDLE: The spindle holds and drives the 
various cutting tools. It is a shaft mounted on 
bearings supported by the column. The spindle 
is driven by an electric motor through a train of 
gears, all mounted within the column. The front 
end of the spindle, which is near the table, has 
an internal taper machined in it. The internal taper 
(3 1/2 inches per foot) permits you to mount 
tapered-shank cutter holders and cutter arbors. 
Two keys, located on the face of the spindle, 
provide a positive drive for the cutter holder, or 
arbor. You secure the holder or arbor in the 
spindle by a drawbolt and jamnut, as shown in 
figure 11-7. Large face mills are sometimes 
mounted directly to the spindle nose. 



J AMNUT 



wilriilililili 



J 



DRAWBOLT 



ARBOR SHANK 



SPINDLE 




OVERARM: The overarm is the horizontal 
beam to which you fasten the arbor support. The 
overarm may be a single casting that slides in 
dovetail ways on the top of the column (fig. 11-6) 
or it may consist of one or two cylindrical bars 
that slide through holes in the column, as shown 
in figure 11-6. To position the overarm on some 
machines, you first unclamp locknuts and then 
extend the overarm by turning a crank. On others, 



TOOLMAKERS UNIVERSAL VISE 




you move the overarm by simply pushing on it. 
You should extend the overarm only far enough 
to position the arbor support to make the setup 
as rigid as possible. To place arbor supports on 
an overarm such as the one shown as B, in figure 
11-6, extend one of the bars approximately 1 inch 
farther than the other bar. Tighten the locknuts 
after positioning the overarm. On some milling 
machines the coolant supply nozzle is fastened to 
the overarm. You can mount the nozzle with a 
split clamp to the overarm after you have placed 
the arbor support in position. 

ARBOR SUPPORT: The arbor support is a 
casting that contains a bearing which aligns the 
outer end of the arbor with the spindle. This helps 
to keep the arbor from springing during cutting 
operations. Two types of arbor supports are 
commonly used. One type has a small diameter 
bearing hole, usually 1-inch maximum diameter. 
The other type has a large diameter bearing hole, 
usually up to 2 3/4 inches. An oil reservoir in the 
arbor support keeps the bearing surfaces 
lubricated. You can clamp an arbor support at 
any place you want on the overarm. Small arbor 
supports give additional clearance below the 
arbor supports when you are using small diameter 
cutters. However, small arbor supports can 
provide support only at the extreme end of the 
arbor. For this reason they are not recommended 
for general use. Large arbor supports can provide 
support near the cutter, if necessary. 

NOTE: Before loosening or tightening the 
arbor nut, you must install the arbor support. This 
will prevent bending or springing of the arbor. 

SIZE DESIGNATION: All milling machines 
are identified by four basic factors: size, 
horsepower, model, and type. The size of a milling 
machine is based on the longitudinal (from left 
to right) table travel in inches. Vertical, cross, and 
longitudinal travel are all closely related as far as 
overall capacity is concerned. For size designa- 
tion, only the longitudinal travel is used. There 
are six sizes of knee-type milling machines, with 
each number representing the number of inches 
of travel. 



BROWN & SHARPE Manufacturing Company, North Kingstown, RJ 

28.199X 
Figure 11-8. Milling machine vises. 



Standard Size 
No. 1 
No. 2 
No. 3 
No. 4 
No. 5 
No. 6 



Longitudinal Table Travel 
22 inches 
28 inches 
34 inches 
42 inches 
50 inches 
60 inches 



11-6 



brands. The TYPE of milling machine is 
designated as plain or universal, horizontal or 
vertical, and knee and column or bed. In 
addition, machines may have other special type 
designations. 

Standard equipment used with milling 
machines in Navy ships includes workholding 
devices, spindle attachments, cutters, arbors, and 
any special tools needed for setting up the 
machines for milling. This equipment allows you 
to hold and cut the great variety of milling jobs 
you will encounter in Navy repair work. 

WORKHOLDING DEVICES 

The following workholding devices are the 
ones that you will probably use most frequently. 



vise provides the most support for a rigid 
workpiece. The swivel vise is similar to the flanged 
vise, but the setup is less rigid because the 
workpiece can be swiveled in a horizontal plane 
to any required angle. The toolmaker's universal 
vise provides the least rigid support because it is 
designed to set up the workpiece at a complex 
angle in relation to the axis of the spindle and to 
the surface of the table. 

INDEXING EQUIPMENT 

Indexing equipment (fig. 11-9) is used to hold 
and turn the workpiece so that a number of 
accurately spaced cuts can be made (gear teeth for 
example). The workpiece may be held in a chuck 
or a collet, attached to the dividing head spindle, 
or held between a live center in the dividing 







~' - "r. j .":'.r.'".':".:::r" 




CENTER REST| 



BRACKETS FOR 
MOUNTING CHANGE 
GEARS 



DIVIDING 

HEAD 
CENTER 




[FOOTSTOCK] 



[INDEX PLATES 



CHANGE GEARS! 



BROWN & SHARPS Manufacturing Company, North Kingstown, RI 

28.200X 



Figure 11-9. Indexing equipment. 

11-7 



index head and a dead center in the footstock. 
The center of the footstock can be raised or 
lowered for setting up tapered workpieces. The 
center rest can be used to support long slender 
work. 

Dividing Head 

The internal components of the dividing head 
are shown in figure 11-10. The ratio between the 
worm and the gear is 40 to 1. By turning the 
worm one turn, you rotate the spindle 1/40 of a 
revolution. The index plate has a series of 
concentric circles of holes, which you can use to 
gauge partial turns of the worm shaft and to turn 
the spindle accurately in amounts smaller than 
1/40 of a revolution. You can secure the index 
plate either to the dividing head housing or to a 
rotating shaft and you can adjust the crankpin 
radially for use in any circle of holes. You can 
also set the sector arms as a guide to span any 
number of holes in the index plate to provide a 
guide for rotating the index crank for partial 
turns. To rotate the workpiece, you can turn the 
dividing head spindle either directly by hand by 
disengaging the worm and drawing the plunger 
back* or by the index crank through the worm 
and worm gear. 

The spindle is set in a swivel block so that you 
can set the spindle at any angle from slightly below 
horizontal to slightly past vertical. As mentioned 
previously, most index heads have a 40:1 ratio. 
One well-known exception has a 5 to 1 ratio 
(see fig. 11-11). This ratio is made possible by a 
5 to 1 gear ratio between the index crank and the 
dividing head spindle. The faster movement of the 
spindle with one turn of the index crank permits 
speedier production. It is also an advantage in 
truing work or testing work for run out with a 
dial indicator. Although made to a high standard 



SECTOR ARM 



DIVIDING 
HEAD SPINDLE 




WORM GEAR 
(40 TEETH) 



WORM 



SECTOR ARM 



INDEX > WORM 

PLATE SHAFT 




Photo courtesy of Kearney & Trecker Corporation, Milwaukee, Wis. 

28.368X 

Figure 11-11. Universal spiral dividing head with a 
5 to 1 ratio between the spindle and the index crank. 



of accuracy, the 5 to 1 ratio dividing head 
does not permit as wide a selection of 
divisions by simple indexing. Differential indexing 
(discussed later in this chapter) can be done on 
the 5 to 1 ratio dividing head by using a 
differential indexing attachment. 




LEAD 
SCREW 



Fieure 11-10. Dividino head mechanism. 



Fiaure 11-12.- 



28.307X 
-Enclosed drivinc mechanism. 



the work as required for helical and spiral 
milling. The index head may have one of several 
driving mechanisms. The most common of these 
is the ENCLOSED DRIVING MECHANISM, 
which is standard equipment on some makes of 
plain and universal knee and column milling 
machines. The enclosed driving mechanism has 
a lead range of 2 1/2 to 100 inches and is driven 
directly from the lead screw. 

Gearing Arrangement 

Figure 11-12 illustrates the gearing arrange- 
ment used on most milling machines. The gears 
are marked as follows: 

A = Gear on the worm shaft (driven) 
B = First gear on the idler stud (driving) 



E and F = Idler gears 

LOW LEAD DRIVE. For some models and 
makes of milling machines a low lead driving 
mechanism is available; however, additional parts 
must be built into the machine at the factory. This 
driving mechanism has a lead range of 0.125 to 
100 inches. 

LONG AND SHORT LEAD DRIVE. 

When an extremely long or short lead is required, 
you can use the long and short lead attachment 
(fig. 11-13). As with the low lead driving 
mechanism, the milling machine must have 
certain parts built into the machine at the factory. 
In this attachment, an auxiliary shaft in the table 
drive mechanism supplies power through the gear 




BROWN & SHARPE Manufacturing Company, North Kingstown, Rl 

126.27X 



Figure 11-13. The long and short lead attachment. 
11-9 



train to the dividing head. It also supplies the 
power for the table lead screw which is disengaged 
from the regular drive when the attachment is 
used. This attachment provides leads in the range 
between 0.010 and 1000 inches. 

CIRCULAR MILLING ATTACHMENT. 

The circular milling attachment, or rotary table 



(fig. 11-14), is used for setting up work that 
must be rotated in a horizontal plane. The 
worktable is graduated (1/2 to 360) around its 
circumference. You can turn the table by 
hand or by the table feed mechanism through 
a gear train (fig. 11-14). An 80 to 1 worm 
and gear drive contained in the rotary table 
and index plate arrangement makes this device 




BROWN & SHARPS Manufacturing Company, North Kingstown, RI 



SPECIAL ATTACHMENTS 

The universal milling (head) attachment, 
shown in figure 11-15, is clamped to the column 
of the milling machine. The cutter can be secured 
in the spindle of the attachment and then can be 
set by the two rotary swivels so that the cutter will 



ment is driven by gearing connected to the milling 
machine spindle. 

SLOTTING ATTACHMENT 

Although special machines are designed for 
cutting slots (such as key ways and splines), this 
type of machine frequently is not available. 
Consequently, the machinist must devise other 
means for cutting slots. The slotting attachment 



CIRCULAR 

MILLING 

ATTACHMENT 

(ROTARY TABLE) 




28.202X 



Figure 11-15. Circular milling attachments (rotary table) and universal (head) attachment. 



11-11 



in figure 11-16, when mounted on the column and 
the spindle of a plain or universal milling machine, 
will perform such operations. 

The attachment is designed so that the rotating 
motion of the spindle is changed to reciprocating 
motion of the tool slide on the slotter, similar to 
the ram on a shaper. A single point cutting tool 
is used. Since the tool slide can be swiveled 
through 360, slotting can be done at any angle, 
and the stroke can be set to from to 4 inches. 



INDEXING THE WORK 

Indexing is done by the direct, plain, 
compound, or differential method. The direct and 
plain methods are the most commonly used; the 
compound and differential methods are used only 
when the job cannot be done by plain or direct 
indexing. 




DIRECT INDEXING 

Direct indexing, sometimes referred to as rapid 
indexing, is the simplest method of indexing. 
Figure 1 1-17 shows the front index plate attached 
to the work spindle. The front index plate usually 
has 24 equally spaced holes. These holes can be 
engaged by the front index pin, which is spring- 
loaded and moved in and out by a small lever. 
Rapid indexing requires that the worm and the 
worm wheel be disengaged so that the spindle can 
be moved by hand. Numbers that can be divided 
into 24 can be indexed in this manner. Rapid in- 
dexing is used when a large number of duplicate 
parts are to be milled. 

To find the number of holes to move the 
index plate, divide 24 by the number of divisions 
required. 

Number of holes to move = 24/N where 
N = required number of divisions 

Example: Indexing for a hexagon head bolt: 
because a hexagon head has six flats, 

~ = 24 = 4 holes 
N 6 

IN ANY INDEXING OPERATION AL- 
WAYS START COUNTING FROM THE 
HOLE ADJACENT TO THE CRANKPIN. 
During heavy cutting operations, clamp the 
spindle by the clamp screw to relieve strain on the 
index pin. 




BROWN & SHARPS Manufacturing Company, North Kingstown, RI 

28.369X 

Figure 11-16. Slotting a bushing using a slotting 
attachment. 



BROWN & SHARPE Manufacturing Company, North Kingstown, R. 

28.2093 
Figure 11-17. Direct index plate. 



PLAIN INDEXING 

Plain indexing, or simple indexing, is used 
when a circle must be divided into more parts than 
is possible by rapid indexing. Simple indexing 
requires that the spindle be moved by turning an 
index crank, which turns the worm that is meshed 
with the worm wheel. The ratio between worm 
and the worm wheel is 40 to 1 (40:1). One turn 
of the index crank turns the index head spindle 
1/40 of a complete turn. Therefore, forty turns 
of the index crank are required to revolve the 
spindle chuck and the job one complete turn. To 
determine the number of turns or fractional parts 
of a turn of the index crank necessary to cut any 
required number of divisions, divide 40 by the 
number of divisions required. 

40 
Number of turns of the index crank = -rr 

where N = number of divisions required 
Example (1): Index for five divisions 



40 40 Q . 
N" ~ T turns 



There are eight turns of the crank for each 
division. 

Example (2): Index for eight divisions 
40 40 



N 8 



5 turns 



Example (3): Index for ten divisions 

40 40 , , 
N = 10 = 4 turns 

When the number of divisions required does 
not divide evenly into 40, the index crank must 
be moved a fractional part of a turn with index 
plates. A commonly used index head comes with 
three index plates. Each plate has six circles of 
holes which we shall use as an example. 

Plate one: 15-16-17-18-19-20 
Plate two: 21-23-27-29-31-33 
Plate three: 37-39-41-43-47-49 
The previous examples of using the indexing 



the index crank. This seldom happens on the 
typical indexing job. For example, indexing for 
18 divisions 

40 40 ~4 . 

N = 18 = 2 18 turns 

The whole number indicates the complete 
turns of the index crank, the denominator of the 
fraction represents the index circle, and the 
numerator represents the number of holes to use 
on that circle. Because there is an 18-hole index 
circle, the mixed number 2 4/18 indicates that the 
index crank will be moved 2 full turns plus 4 holes 
on the 18-hole circle. The sector arms are 
positioned to include 4 holes and the hole in which 
the index crank pin is engaged. The number of 
holes (4) represents the movement of the index 
crank; the hole that engages the index crank pin 
is not included. 

When the denominator of the indexing 
fraction is smaller or larger than the number of 
holes contained in any of the index circles, change 
it to a number representing one of the circles of 
holes. Do this by multiplying or dividing the 
numerator and the denominator by the same 
number. For example, to index for the machining 
of a hexagon (N = 6): 



4Q = 40 3 = 120 
6 63 18 



12 2 
= 6 turns 



The denominator 3 will divide equally into the 
following circles of holes, so you can use any plate 
that contains one of the circles. 

Plate one: 15 and 18 
Plate two: 21 and 33 
Plate three: 39 

To apply the fraction 2/3 to the circle you choose, 
convert the fraction to a fraction that has the 
number of holes in the circle as a denominator. 
For example, if you choose the 15 hole circle, the 
fraction 2/3 becomes 10/15. If plate 3 happens 
to be on the index head, multiply the denominator 
3 by 13 to equal 39. In order not to change the 
value of the original indexing fraction, also 
multiply the numerator by 13 

2 X 13 = 26 
3 13 39 

The original indexing rotation of 6 2/3 turns 



full turns and 26 holes on the 39-hole circle. 

When the number of divisions exceeds 40, 
you may divide both the numerator and the 
denominator of the fraction by a common divisor 
to obtain an index circle that is available. For 
example, if 160 divisions are required, N = 160; 
the fraction to be used is 



40 

N 



_ 

160 



Because there is no 160-hole circle this fraction 
must be reduced. To use a 16-hole circle, divide 
the numerator and denominator by 10. 

40/10 4 



160/10 16 
Turn 4 holes on the 16-hole circle. 

It is usually more convenient to reduce the 
original fraction to its lowest terms and then 
multiply both terms of the fraction by a factor 
that will give a number representing a circle of 
holes. 



40 
160 



4 4" 16 

The following examples will further clarify the 
use of this formula: 

Example 1: Index for 9 divisions. 

40 = 40 _ A 
N 9 4 9 

If an 18-hole circle is used, the fraction 
becomes 4/9 x 2/2 = 8/18. For each division, 
turn the crank 4 turns and 8 holes on an 18-hole 
circle. 

Example 2: Index for 136 divisions. 



4C I 

N 



40 5 
136 17 



There is a 17-hole circle, so for each division 
turn the crank 5 holes on a 17-hole circle. 



In setting the sector arms to space off the 
required number of holes on the index 
circle, do not count the hole that the 
index crank pin is in. 

Most manufacturers provide different plates 
for indexing. Later model Brown and Sharpe 
index heads use two plates with the following 
circle of holes: 

Plate one: 15, 16, 19, 23, 31, 37, 41, 43, 47 
Plate two: 17, 18, 20, 21, 27, 29, 33, 39, 47 

The standard index plate supplied with the 
Cincinnati index head is provided with 1 1 different 
circles of holes on each side. 

Side one: 24-25-28-30-34-37-38-39-4-42-43 
Side two: 46-47-49-51-53-54-57-58-59-62-66 

ANGULAR INDEXING 

When you must divide work into degrees or 
fractions of a degree by plain indexing, remember 
that one turn of the index crank will rotate a point 
on the circumference of the work 1/40 of a revolu- 
tion. Since there are 360 in a circle, one turn of 
the index crank will revolve the circumference of 
the work 1 /40 of 360 , or 9 . Hence, in using the 
index plate and fractional parts of a turn, 2 holes 
in an 18-hole circle equal 1 (1/9 turn x 9/turn), 
1 hole in a 27-hole circle equals 1/3 (1/27 
turn x 9/turn), 3 holes in a 54-hole circle equal 
1/2 (1/18 turn x9/turn). To determine the 
number of turns and parts of a turn of the index 
crank for a desired number of degrees, divide the 
number of degrees by 9. The quotient will 
represent the number of complete turns and 
fractions of a turn that you should rotate the 
index crank. For example, the calculation for 
determining 15 when an index plate with a 
54-hole circle is available, is as follows: 



36 



or one complete turn plus 36 holes on the 54-hole 
circle. The calculation for determining 13 1/2 



11-14 



or one complete turn plus 9 holes on the 18-hole 
circle. 

When indexing angles are given in minutes, 
and approximate divisions are acceptable, move- 
ment of the index crank and the proper index plate 
may be determined by the following calculations. 
You can determine the number of minutes 
represented by one turn of the index crank by 
multiplying the number of degrees covered in one 
turn of the index crank by 60 minutes/degree. 

9 x 60 min/degree = 540 min 

Therefore, open turn of the index crank will rotate 
the index head spindle 540 minutes. 

The number of minutes (540) divided by 
the number of minutes in the division desired, 
indicates the total number of holes there 
should be in the index plate used. (Moving 
the index crank one hole will rotate the index 
head spindle through the desired number of 
minutes of angle.) This method of indexing 
can be used only for approximate angles since 
ordinarily the quotient will come out in mixed 
numbers or in numbers for which there are 
no index plates available. However, when the 
quotient is nearly equal to the number of 
holes in an available index plate, the nearest 
number of holes can be used and the error 
will be very small. For example the calculation 
for 24 minutes would be: 



540 

24 



22.5 
1 



or one hole on the 22.5 hole circle. Since there 
is no 22.5-hole circle on the index plate, a 23-hole 
circle plate would be used. 

If a quotient is not approximately equal 
to an available circle of holes, multiply by 
any trial number which will give a product 
equal to the number of holes in one of the 
available index circles. You can then move 
the crank the required number of holes to 
give the desired division. For example, the 
calculation for determining 54 minutes when 



540 10 2 20 (20-hole circle) 
or 2 holes on the 20-hole circle. 

COMPOUND INDEXING 

Compound indexing is a combination of two 
plain indexing procedures. One number of 
divisions is indexed using the standard plain 
indexing method; another number of divisions is 
indexed by turning the index plate (leaving the 
crank pin engaged in the hole as set in the first 
indexing operation) by a required amount. The 
difference between the amount indexed in the first 
operation and the amount indexed in the second 
operation results in the spindle turning the 
required amount for the number of divisions. 
Compound indexing is seldom used because (1) 
differential indexing is easier, (2) high number 
index plates are usually available to provide any 
range of divisions normally required and (3) the 
computation and actual operation are quite 
complicated, making it easy for errors to be 
introduced. 

Compound indexing is briefly described in the 
following example. To index 99 divisions proceed 
as follows: 

1 . Multiply the required number of divisions 
by the difference between the number of holes in 
two circles selected at random. Divide this 
product by 40 (ratio of spindle to crank) times 
the product of the two index hole circles. Assume 
that the 27-hole circle and 3 3 -hole circle have been 
selected. The resulting equation is: 

99 x (33 - 27) 99 x 6 

40 x 33 x 27 40 x 33 x 27 

2. To make the problem easier to solve, 
factor each term of the equation into its lowest 
prime factors and cancel where possible. For 
example: 



(2 x 



x 2) 



(2 x 2 x 2 x 5)(17 x 2f)(3 x 2 x 3) 60 

The result of this process must be in the form of 
a fraction as given (that is, 1 divided by some 
number). Always try to select the two circles which 



11-15 



have factors that will cancel out the factors in the 
numerator of the problem. When the numerator 
of the resulting fraction is greater than 1 , divide 
it by the denominator and use the quotient (to 
nearest whole number) instead of the denominator 
of the fraction. 

3. The denominator of the resulting fraction 
derived in step two is the term used to find the 
number of turns and holes for indexing the spindle 
and index plate. To index for 99 divisions, turn 
the spindle by an amount equal to 60/33 or one 
complete turn plus 27 holes in the 33-hole circle; 
turn the index plate by an amount equal to 60/27, 
or two complete turns plus 6 holes in the 27-hole 
circle. If you turn the index crank clockwise, turn 
the index plate counterclockwise and vice versa. 



DIFFERENTIAL INDEXING 

Differential indexing is similar to compound 
indexing except that the index plate is turned 
during the indexing operation by gears connected 
to the dividing head spindle. Because the index 
plate movement is caused by the spindle move- 
ment, only one indexing procedure is required. 
The gear train between the dividing head spindle 
and the index plate provides the correct ratio of 
movement between the spindle and the index 
plate. 

Figure 11-18 shows a dividing head set up for 
differential indexing. The index crank is turned 
as it is for plain indexing, thus turning the spindle 
gear and then the compound gear and the idler 
to drive the gear which turns the index plate. 
Specific procedures for installing the gearing 
and arranging the index plate for differential in- 
dexing (and compound indexing) are given in 
manufacturers' technical manuals. 

To index 57 divisions, for example, take the 
following steps: 

1 . Select a number greater or lesser than the 
required number of divisions for which an 
available index plate can be used (60 for example). 

2. The number of turns for plain indexing 60 
divisions is: 40/60 or 14/21, which will require 
14 holes in a 21 -hole circle in the index plate. 

3. To find the required gear ratio, subtract the 
required number of divisions from the selected 




28.210X 



Figure 11-18. Differential indexing. 



number or vice versa (depending on which is 
larger), and multiply the result by 40/60 (formula 
for indexing 60 divisions). Thus: 



gear ratio = (60 - 57) x = 



The numerator indicates the spindle gear; the 
denominator indicates the driven gear. 

4. Select two gears that have a 2 to 1 ratio (for 
example a 48-tooth gear and a 24-tooth gear). 

5 . If the selected number is greater than the 
actual number of divisions required, use one or 
three idlers in the simple gear train; if the selected 
number is smaller, use none or two idlers. The 
reverse is true for compound gear trains. Since 
the number is greater in this example, use one or 
three idlers. 

6. Now turn the index crank 14 holes in the 
21-hole circle of the index plate. As the crank 
turns the spindle, the gear train turns the index 
plate slightly faster than the index crank. 

Wide Range Divider 

In the majority of indexing operations, you 
can get the desired number of equally spaced 
divisions by using either direct or plain indexing. 



11-16 



By using one or the other of these methods, you 
may index up to 2,640 divisions. To increase the 
range of divisions, use the high number index 
plates in place of the standard index plate. These 
high number plates have a greater number of 
circles of holes and a greater range of holes in the 
circles than the standard plates. This increases the 
range of possible divisions from 1,040 to 7,960. 

In some instances, you may need to index 
beyond the range of any of these methods. To 
further increase the range, use a universal dividing 
head that has a wide range divider. This type of 
indexing equipment enables you to index divisions 
from 2 to 400,000. The wide range divider (Fig. 
11-19) consists of a large index plate with sector 
arms and a crank and a small index plate with 
sector arms and a crank. The large index plate 
(A, fig 11-19) has holes drilled on both sides and 
contains eleven circles of holes on each side of 
the plate. The number of holes in the circles on 
one side are 24, 28, 30, 34, 37, 38, 39, 41, 42, 43, 
and 100. The other side of the plate has circles 
containing 46, 47, 49, 51, 53, 54, 57, 58, 59, 62, 
and 66 holes. The small index plate has two circles 



of holes and is drilled on one side only. The outer 
circle has 100 holes and the inner circle has 54 
holes. 

The small index plate (C, fig. 11-19) is 
mounted on the housing of the planetary gearing 
(G, fig. 11-19), which is built into the index crank 
(B, fig. 11-19) of the large plate. As the index 
crank of the large plate is rotated, the planetary 
gearing assembly and the small index plate and 
crank rotate with it. 

As with the standard dividing head, the large 
index crank rotates the spindle in the ratio of 40 
to 1 . Therefore, one complete turn of the large 
index crank rotates the dividing head spindle 1/40 
of a turn, or 9 . By using the large index plate 
and the crank, you can index in the conventional 
manner. Machine operation is the same as it is 
with the standard dividing head. 

When the small index crank (D, fig. 11-19) is 
rotated, the large index crank remains stationary 
but the main shaft that drives the work revolves 
in the ratio of 1 to 100. This ratio, superimposed 
on the 40 to 1 ratio between the worm and worm 




Figure 11-19. The wide range divider. 



126.28X 



wheel (fig. 1 1-20), causes the dividing head spindle 
to rotate in the ratio of 4,000 to 1. This means 
that one complete revolution of the spindle will 
require 4,000 turns of the small index crank. 
Turning the small crank one complete turn will 
rotate the dividing head spindle 5 minutes, 24 
seconds of a degree. If one hole of the 100-hole 
circle on the small index plate were to be indexed, 
the dividing head spindle would make 1/400,000 
of a turn, or 3.24 seconds of a degree. 

You can get any whole number of divisions 
up to and including 60, and hundreds of others, 
by using only the large index plate and the crank. 
The dividing head manufacturer provides tables 
listing many of the settings for specific divisions 
that may be read directly from the table with no 
further calculations necessary. If the number of 
divisions required is not listed in the table or if 
there are no tables, use the manufacturer's manual 
or other reference for instructions on how to 
compute the required settings. 

Adjusting the Sector Arms 

To use the index head sector arms, turn the 
left-hand arm to the left of the index pin, which 
is inserted into the first hole in the circle of holes 
that is to be used. Then loosen the setscrew (fig. 
11-19E) and adjust the right-hand arm of the 



sector so that the correct number of holes will be 
contained between the two arms (fig. 11-21). After 
making the adjustments, lock the setscrew to hold 
the arms in position. When setting the arms, count 
the required number of holes from the one in 
which the pin is inserted, considering this hole as 
zero. By subsequent use of the index sector, you 
will not need to count the holes for each division. 
When using the index crank to revolve the spindle, 
you must unlock the spindle clamp screw; 
however, before cutting work held in or on the 
index head, lock the spindle again to relieve the 
strain on the index pin. 



CUTTERS AND ARBORS 

When you perform a milling operation, you 
move the work into a rotating cutter. On most 
milling machines, the cutter is mounted on an 
arbor that is driven by the spindle. However, the 
spindle may drive the cutter directly. We will 
discuss cutters in the first part of this section and 
arbors in the second part. 

CUTTERS 

There are many different milling machine 
cutters. Some cutters can be used for several 



CLAMPING STRAPS 
SWIVEL BLOCK 



INDEX- PIN INDEX CRANK 



ECCENTRIC 

FOR 

DISENGAGING 
WORM 




TRUNNION 

INDEX PLATE 



\ 



INDEX PLATE 
STOP PIN 



INDEX 
CRANK 




WORM 
SHAFT NUT 



INDEX PLATE 



28.371X 

Figure 11-21. Principal parts of a late model Cincinnati 
universal spiral index head. 



operations, while others can be used for only one 
operation. Some cutters have straight teeth and 
others have helical teeth. Some cutters have 
mounting shanks and others have mounting holes. 
You must decide which cutter to use. To make 
this decision, you must be familiar with the 
various milling cutters and their uses. The 
information in this section will help you to select 
the proper cutter for each of the various 
operations you will perform. In this section we 
will cover cutter types and cutter selection. 

Standard milling cutters are made in many 
shapes and sizes for milling both regular and 
irregular shapes. Various cutters designed for 
specific purposes also are available; for example, 



a cutter for milling a particular kind of curve on 
some intermediate part of the workpiece. 

Milling cutters generally take their names from 
the operation that they perform. The most 
common cutters are: (1) plain milling cutters of 
various widths and diameters, used principally for 
milling flat surfaces that are parallel to the axis 
of the cutter: (2) angular milling cutters, designed 
for milling V-grooves and the grooves in reamers, 
taps, and milling cutters; (3) face milling cutters, 
used for milling flat surfaces at a right angle to 
the axis of the cutter; and (4) forming cutters, used 
to produce surfaces with an irregular outline. 

Milling cutters may also be classified as arbor- 
mounted, or shank-mounted. Arbor-mounted 
cutters are mounted on the straight shanks of 
arbors. The arbor is then inserted into the milling 
machine spindle. We will discuss the methods of 
mounting arbors and cutters in greater detail later 
in this chapter. 

Milling cutters may have straight, right-hand, 
left-hand, or staggered teeth. Straight teeth are 
parallel to the axis of the cutter. If the helix angle 
twists in a clockwise direction (viewed from either 
end), the cutter has right-hand teeth. If the helix 
angle twists in a counterclockwise direction, the 
cutter has left-hand teeth. The teeth on staggered- 
tooth cutters are alternately left-hand and right- 
hand. 

Types and Uses 

There are many different types of milling 
cutters. We will now discuss these types and their 
uses. 

PLAIN MILLING CUTTER. You will use 
plain milling cutters to mill flat surfaces that are 
parallel to the cutter axis. As you can see in figure 
1 1-22, a plain milling cutter is a cylinder with teeth 






28.372 



SmiWA 11 _'>} Dlain millinn 



cut on the circumference only. Plain milling 
cutters are made in a variety of diameters and 
widths. Note in figure 11-23, that the cutter teeth 
may be either straight or helical. When the width 
is more than 3/4 inch, the teeth are usually helical. 
The teeth of a straight cutter tool are parallel to 
axis of the cutter. This causes each tooth to cut 
along its entire width at the same time, causing 
a shock as the tooth starts to cut. Helical teeth 



eliminate this shock and produce a free cutting 
action. A helical tooth begins .the cut at one end 
and continues across the work with a smooth 
shaving action. Plain milling cutters usually have 
radial teeth. On some coarse helical tooth cutters 
the tooth face is undercut to produce a smoother 
cutting action. Coarse teeth decrease the tendency 
of the arbor to spring and give the cutter greater 
strength. 



RADIAL RELIEF 
ANGLE 



CLEARANC SURFACE 
LAND 

HEEL 
FLUTE 

TOOTH 




RADIAL RAKE ANGLE 
(POSITIVE SHOWN) 



OFFSET 



PERIPHERAL 
CUTTING EDGE 



TOOTH FACE 



CLEARANCE 
SURFACE 



CONCAVITY 




AXIAL RELIEF 
ANGLE 



FILLET 



LIP ANGLE 





HELICAL TEETH 



HELICAL RAKE ANGLE 
(LH HELIX SHOWN } 



RADIAL RAKE ANGLE 
(POSITIVE SHOWN)' 



RADIAL RELIEF 
TOOTH 



FILLET 




TOOTH FACE 



AXIAL RELIEF 




OFFSET 



A plain milling cutter has a standard size 
arbor hole for mounting on a standard size 
arbor. The size of the cutter is designated by the 
diameter and width of the cutter, and the diameter 
of the arbor hole in the cutter. 

SIDE MILLING CUTTER. The side milling 
cutter (fig. 11-24) is a plain milling cutter with 
teeth cut on both sides as well as on the periphery 
or circumference of the cutter. You can see that 
the portion of the cutter between the hub and the 
side of the teeth is thinner to give more chip 
clearance. These cutters are often used in pairs 
to mill parallel sides. This process is called straddle 
milling. Cutters more than 8 inches in diameter 
are usually made with inserted teeth. The size 
designation is the same as for plain milling cutters. 

HALF-SIDE MILLING CUTTER. Half- 
side milling cutters (fig. 11-25) are made 
particularly for jobs where only one side of the 
cutter is needed. These cutters have coarse, helical 
teeth on one side only so that heavy cuts can be 
made with ease. 





SIDE MILLING CUTTER (INTERLOCK- 
ING). Side milling cutters whose teeth interlock 
(fig. 1 1-26) can be used to mill standard size slots. 
The width is regulated by thin washers inserted 
between the cutters. 

METAL SLITTING SAW. You can use a 
metal slitting saw to cut off work or to mill 
narrow slots. A metal slitting saw is similar to a 
plain or side milling cutter, with a face width 
usually less than 3/16 inch. This type of cutter 
usually has more teeth for a given diameter than 
a plain cutter. It is thinner at the center than at 
the outer edge to give proper clearance for milling 




Figure 11-25. Half-side milling cutter. 





Figure 11-24. Side milling cutter. 



Figure 11-26. Interlocking teeth side milling cutter. 



deep slots. Figure 11-27 shows a metal slitting saw 
with teeth cut in the circumference of the cutter 
only. Some saws, such as the one in figure 1 1-28, 
have side teeth which achieve better cutting 
action, break up chips, and prevent dragging when 
you cut deep slots. For heavy sawing in steel, there 
are metal slitting saws with staggered teeth, as 
shown in figure 11-29. These cutters are usually 
3/16 inch to 3/8 inch thick. 

SCREW SLOTTING CUTTER. The screw 
slotting cutter (fig. 11-30) is used to cut shallow 
slots, such as those in screw heads. This cutter 
has fine teeth cut on its circumference. It is made 
in various thicknesses to correspond to American 
Standard gauge wire numbers. 

ANGLE CUTTER.- Angle cutters are used 
to mill surfaces that are not at a right angle to 




Figure 11-27. Metal slitting saw. 







Figure 11-29. Slitting saw with staggered teeth. 





Figure 11-30. Screw slotting cutter. 





Figure ll-28.-Slitting saw with side teeth. Figure ll-31.-Single angle cutter. 

11-22 



cutter axis. You can use angle cutters for a variety 
of work, such as milling V-grooves and dovetail 
ways. On work such as dovetailing, where you 
cannot mount a cutter in the usual manner on an 
arbor, you can mount an angle cutter that has a 
threaded hole, or is constructed like a shell end 





Figure 11-32. Double angle cutter. 



mill, on the end of a stub or shell end mill 
arbor. When you select an angle cutter for a job 
you should specify the type, hand, outside 
diameter, thickness, hole size, and angle. 

There are two types of angle cutters single 
and double. The single angle cutter, shown in 
figure 1 1-31, has teeth cut at an oblique angle with 
one side at an angle of 90 to the cutter axis and 
the other usually at 45, 50, or 80. 

The double angle cutter (fig. 11-32) has two 
cutting faces, which are at an angle to the cutter 
axis. When both faces are at the same angle to 
the axis, you obtain the cutter you want by 
specifying the included angle. When they are 
different angles, you specify the angle of each side 
with respect to the plane of intersection. 

FLUTING CUTTER. A fluting cutter is a 
double angle form tooth cutter with the points of 
the teeth well rounded. It is generally used to mill 
flutes in reamers. Fluting cutters are marked with 
the range of diameters they are designed to mill. 

END MILL CUTTERS. End mill cutters 
may be the SOLID TYPE with the teeth and the 
shank as an integral part (fig. 1 1-33), or they may 






(A) Two-flute single-end; (B) Two-flute double-end; Carbide-tipped, straight flutes; (H) Carbide-tipped, RH 
(C) Three-flute single-end; (D) Multiple-flute single-end; helical flutes; (I) Multiple-flute with toper shank; (J) 
(E) Four-flute double-end; (F) Two -flute ball-end; (G) Carbide -tipped with taper shank and helical flutes. 




Figure 11-34. Shell end mill. 



be the SHELL TYPE (fig. 11-34) in which the 
cutter body and the shank or arbor are separate. 
End mill cutters have teeth on the circumference 
and on the end. Those on the circumference may 
be either straight or helical (fig. 11-35). 

Except for the shell type, all end mills have 
either a straight shank or a tapered shank which 
is mounted into the spindle of the machine for 



STANDARD 
MILLING CUTTERS AND END MILLS 



LENGTH OF OVERALL 




END CUTTING EDGE 
CONCAVITY ANGLE 



TOOTH FACE 



^J N\ 




RADIAL RAKE ANGLE 
(POSITIVE SHOWN) 



END CLEARANCE 



AXIAL 
RELIEF ANGLE 



END GASH 



HELIX ANGLE 




TOOTH FACE 



C RADIAL 
JUTTING EDGE 



FLUTE 



ENLARGED SECTION 
OF END MILL 



RADIAL LAND 




RADIAL CLEARANCE ANGLE 



ENLARGED SECTION 
nr Fwn MII i rnnrw 



driving the cutter. There are various types of 
adapters for securing end mills to the machine 
spindle. 

End milling involves the machining of surfaces 
(horizontal, vertical, angular, or irregular) with 
end mill cutters. Common operations include the 
milling of slots, keyways, pockets, shoulders, and 
flat surfaces, and the profiling of narrow surfaces. 

End mill cutters are used most often on 
vertical milling machines. However, they also are 
used frequently on machines with horizontal 
spindles. Many different types of end mill cutters 
are available in sizes ranging from 1/64 inch to 
2 inches. They may be made of high-speed steel, 
may have cemented carbide teeth, or may be of 
the solid carbide type. 

TWO-FLUTE END MILLS have only two 
teeth on their circumference. The end teeth can 
cut to the cutter. Hence, they may be fed into the 
work like a drill; they can then be fed lengthwise 
to form a slot. These mills may be either the 
single-end type with the cutter on one end only, 
or they may be the double-end type. (See fig. 
11-33.) 

MULTIPLE-FLUTE END MILLS have 
three, four, six, or eight flutes and normally are 
available in diameters up to 2 inches. They may 
be either the single-end or the double-end type 
(fig. 11-33). 

BALL END MILLS (fig. 1 1-33) are used for 
milling fillets or slots with a radius bottom, for 
rounding pockets and the bottom of holes, and 
for all-around die sinking and die making work. 
Two-flute end mills with end cutting lips can be 
used to drill the initial hole as well as to feed 
longitudinally. Four-flute ball end mills with 
center cutting lips also are available. These work 
well for tracer milling, fillet milling and die 
sinking. 

SHELL END MILLS (fig. 1 1-34) have a hole 
for mounting the cutter on a short (stub) arbor. 
The center of the shell is recessed for the screw 
or nut that fastens the cutter to the arbor. These 
mills are made in larger sizes than solid end mills, 
normally in diameters from 1 1/4 to 6 inches. 
Cutters of this type are intended for slabbing or 
surfacing cuts, either face milling or end milling, 
and usually have helical teeth. 

FACE MILLING CUTTER. Inserted tooth 
face milling cutters (fig. 1 1-36) are similar to shell 




Figure 11-36. Inserted tooth face milling cutter. 



end mills in that they have teeth on the 
circumference and on the end. They are attached 
directly to the spindle nose and use inserted, 
replaceable teeth made of carbide or any alloy 
steel. 

T-SLOT CUTTER. The T-slot cutter 
(fig. 11-37) is a small plain milling cutter 
with a shank. It is designed especially to mill 
the "head space*' of T-slots. T-slots are cut 
in two operations. First, you cut a slot with 
an end mill or a plain milling cutter, and then 
you make the cut at the bottom of the slot 
with a T-slot cutter. 




Figure 11-37. T-slot cutter. 



11-25 





Figure 11-38. Woodruff keyseat cutter. 



Figure 11-40. Concave cutter. 




\jLJ 



Figure 11-39. Involute gear cutter. 





Figure 11-41. Convex cutter. 




Figure 11-42. Corner rounding cutter. 



11-26 



WOODRUFF KEYSEAT CUTTER. A 

Woodruff keyseat cutter (fig. 1 1-38) is used to cut 
curved keyseats. A cutter less than 1 1/2 inches 
in diameter has a shank. When the diameter 
is greater than 1 1/2 inches, the cutter is 
usually mounted on an arbor. The larger cutters 
have staggered teeth to improve the cutting 
action. 

GEAR CUTTERS. There are several types 
of gear cutters, such as bevel, spur, involute, and 
so on. Figure 1 1-39 shows an involute gear cutter. 
You must select the correct type of cutter to cut 
a particular type of gear. 

CONCAVE AND CONVEX CUTTERS. 

A concave cutter (fig. 11-40) is used to mill a 
convex surface, and a convex cutter (fig. 11-41) 
is used to mill a concave surface. 



WIDTH 



KEYWAY 



HOLE 



./""" 



tr 

UJ UJ 

o h- 
^ uj 



05 




Figure 11-43. Sprocketed wheel cutter. 




CORNER ROUNDING CUTTER. -Corner 

rounding cutters (fig. H-42) are formed cutters 
that are used to round corners up to one-quarter 
of a circle. 

SPROCKET WHEEL CUTTER. The 

sprocket wheel cutter (fig. 11-43) is a formed 
cutter that is used to mill teeth on sprocket wheels. 

GEAR HOB. The gear hob (fig. 1 1-44) Is a 
formed milling cutter with teeth cut like threads 
on a screw. 

FLY CUTTER. The fly cutter (fig. 11-45) 
is often manufactured locally. It is a single-point 
cutting tool similar in shape to a lathe or shaper 
tool. It is held and rotated by a fly cutter arbor. 
There will be times when you need a special 
formed cutter for a very limited number of cutting 
or boring operations. This will probably be the 
type of cutter you will use since you can grind it 
to almost any form you desire. 

We have discussed a number of the more 
common types of milling machine cutters. For a 
more detailed discussion of these and other types 
of cutters and their uses, consult the Machinery's 
Handbook^ machinist publications, or the 
applicable technical manual. We will now discuss 
the selection of cutters. 






Figure 11-44. Gear hob. 



Figure 11-45. Fly cutter arbor and fly cutters. 



Naval Education and 
Training Command 



NAVEDTRA 12204 
May 1990 
0502-LP-2 13-11 00 



Training Manual 
(TRAMAN) 




Machinery 
Repairman 3 & 2 



? 

'I 
c 

z 

3 

g 



DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. 



Nonfederal government personnel wanting a copy of this document 
must use the purchasing instructions on the inside cover. 



O 

r 
m 



S/N0502-LP-213-1100 



1 3/4 inches. The numbers representing common 
milling machine spindle tapers and their sizes are 
as follows: 



Number 
10 
20 
30 
40 
50 
60 



Large Diameter 

5/8 inch 

7/8 inch 

11/4 inches 

13/4 inches 

2 3/4 inches 

41/4 inches 



Standard arbors are available in styles A and 
B, as shown in figure 1 1-47. Style A arbors have 
a pilot type bearing usually 11/32 inch in 
diameter. Style B arbors have a sleeve type out- 
board bearing. Numerals identify the outside 
diameter of the bearing sleeves, as follows: 

Sleeve Number Outside Diameter 

3 1 7/8 inches 

4 21/8 inches 

5 23/4 inches 

The inside diameter can be any one of several 
standard diameters that are used for the arbor 
shaft. 

Style A arbors sometimes have a sleeve bearing 
that permits the arbor to be used as either a style 
A or a style B arbor. A code system, consisting 
of numerals and a letter, identifies the size and 
style of the arbor. The code number is stamped 
into the flange or on the tapered portion of the 
arbor. The first number of the code identifies the 
diameter of the taper. The second (and if used, 



the third number) indicates the diameter of the 
arbor shaft. The letter indicates the type of bear- 
ing. The numbers following the letter indicate the 
usable length of the arbor shaft. Sometimes an 
additional number is used to indicate the size of 
sleeve type bearings. The meaning of a typical 
code number 5-1 1/4- A- 18-4 is as follows: 

5 = taper number 50 (the is omitted 
in the code) 

11/4 = shaft diameter 1 1/4 inches 
A = Style A bearing pilot type 
18 = usable shaft length 18 inches 
4 = bearing size 2 1/8 inches diameter 

STUB ARBOR. Arbors that have very short 
shafts, such as .the one shown in figure 11-48, are 
called stub arbors. Stub arbors are used when it 
is impractical to use a longer arbor. 

You will use arbor spacing collars of various 
lengths to position and secure the cutter on the 
arbor. You tighten the spacers against the cutter 
when you tighten the nut on the arbor. 
Remember, never tighten or loosen the arbor nut 
unless the arbor support is in place. 

SHELL END ARBOR. Shell end mill arbors 
(fig. 11-49) are used to hold and drive shell end 
mills. The shell end mill is fitted over the short 
boss on the arbor shaft. It is driven by two keys 
and is held against the face of the arbor by a bolt. 
You use a special wrench, shown in figure 1 1-48, 



ALINEMENT BOSS 



LOCK BOLT 




Figure 11-48. Stub arbor. 



Figure 11-49. Shell end mill arbor. 



to tighten and loosen the bolt. Shell end mill 
arbors are identified by a code similar to the 
standard arbor code. The letter C indicates a shell 
end mill arbor. The meaning of a typical shell mill 
arbor code 4-1 1/2C-7/8 is as follows: 

4 = taper code number 40 

11/2 = diameter of mounting hole in end 
mill 1 1/2 inches 

C = style C arbor shell end mill 
7/8 = length of shaft 7/8 inch 

FLY CUTTER ARBOR. Fly cutter arbors 
are used to hold single-point cutters. These 
cutters, which can be ground to any desired shape 
and held in the arbor by a locknut, are shown in 
figure 11-44. Fly cutter arbor shanks may have 
a standard milling machine spindle taper, a Brown 
and Sharpe taper, or a Morse taper. 

SCREW SLOTTING CUTTER ARBOR. 

Screw slotting cutter arbors are used with screw 
slotting cutters. The flanges support the cutter and 
prevent the cutter from flexing. The shanks on 
screw slotting cutter arbors may be straight or 
tapered, as shown in figure 11-50. 

SCREW ARBOR. Screw arbors (fig. 11-51) 
are used with cutters that have threaded mounting 
holes. The threads may be left- or right-hand. 

TAPER ADAPTER. Taper adapters are 
used to hold and drive taper-shanked tools, such 
as drills, drill chucks, reamers, and end mills, by 
inserting them into the tapered hole in the adapter. 
The code for a taper adapter indicates the number 
representing the standard milling machine spindle 
taper and the number and series of the internal 



n 



r\ 



u 



FOR DRAW-IN ROD 



\- 



TAPER SHANK 





Figure 11-50. Screw slotting cutter arbor. 



Figure 11-51. Screw arbor. 

taper. For example, the taper adapter code 
number 43 M means: 

4 = taper identification number 40 
3M = internal taper number 3 Morse 

If a letter is not included in the code number, the 
taper is understood to be a Brown and Sharpe. 
For example, 57 means: 

5 = taper number 50 

7 = internal taper number 7 B and S 
and 50-10 means: 

50 = taper identification number 

10 = internal taper number 10 B and S 

Figure 11-52 shows a typical taper adapter. 
Some cutter adapters are designed to be used with 
tools that have taper shanks and a cam locking 
feature. The cam lock adapter code indicates the 
number of the external taper, number of the 
internal taper (which is usually a standard milling 
machine spindle taper), and the distance that the 
adapter extends from the spindle of the machine. 
For example, 50-20-3 5/8 inches means: 

50 = taper identification number (external) 
20 = taper identification number (internal) 

35/8 = distance adapter extends from spindle 
is 3 5/8 inches 

CUTTER ADAPTER. Cutter adapters, 
such as shown in figure 1 1-53, are similar to taper 
adapters except that they always have straight, 
rather than tapered holes. They are used to hold 
straight shank drills, end mills, and so on. The 
cutting tool is secured in the adapter by a setscrew. 
The code number indicates the number of the 
taper and the diameter of the hole. For example, 




SPRING COLLET 
ADAPTER 



LOCK NUT 




Figure 11-52. Taper adapter. 



SPANNER WRENCH 



Figure 11-54. Spring collet chuck adapter. 



LOCK SCREW 




ALLEN WRENCH 

Figure 11-53. Cutter adapter. 



50-5/8 means that the adapter has a number 50 
taper and a 5/8-inch-diameter hole. 

SPRING COLLET CHUCK. Spring collet 
chucks (fig. 11-54) are used to hold and drive 
straight-shanked tools. The spring collet chuck 
consists of a collet adapter, spring collets, and a 
cup nut. Spring collets are similar to lathe 
collets. The cup forces the collet into the mating 
taper, causing the collet to close on the straight 
shank of the tool. The collets are available in 
several fractional sizes. 

Mounting and Dismounting Arbors 

Mounting and dismounting arbors are 
relatively easy tasks. Take care not to drop the 
arbor on the milling machine table or the floor. 
Use figure 11-7 as a guide. To MOUNT an 
arbor, use the following procedure: 

1. Place the spindle in the lowest speed. 

2. Disengage the spindle clutch lever. 



3. Turn off the motor switch. 

4. Clean the spindle hole and the arbor 
thoroughly to ensure accurate alignment of the 
arbor inside the spindle. 

5 . Stand near the column at a point where you 
can reach both ends of the milling machine. Align 
the arbor keyseats with the keys in the spindle. 

6. Insert the tapered shank of the arbor into 
the spindle. 

7. Hold the arbor in place with one hand and 
screw the drawbolt into the arbor with your other 
hand. 

NOTE: Turn the drawbolt a sufficient number 
of turns to ensure that the drawbolt extends into 
the arbor shank a distance approximately equal 
to the major diameter of the threads being used. 
This will help to prevent striping the threads on 
the drawbolt or in the arbor shank when the jam- 
nut is tightened. 

8. Hold the arbor in position by pulling back 
on the drawbolt and tighten the jamnut by hand. 

9. Tighten the jamnut with one wrench while 
using a second wrench to keep the drawbolt from 
turning 

To DISMOUNT an arbor, use the following 
procedure: 

1. Place the spindle in the lowest speed. 

2. Turn off the motor. 

3. Loosen the jamnut approximately two 
turns. 

4. Use one wrench to turn the jamnut and 
another wrench to keep the drawbolt from 
turning. 

5. Hold the arbor with one hand and gently 
tap the end of the drawbolt with a lead mallet until 
you feel the arbor break free. 



6. Hold the arbor in place with one hand and 
unscrew the drawbolt with your other hand. 

7. Remove the arbor from the spindle. 



MILLING MACHINE OPERATIONS 

The milling machine is one of the most 
versatile metalworking machines. It is capable of 
performing simple operations, such as milling a 
flat surface or drilling a hole, or more complex 
operations, such as milling helical gear teeth. It 
would be impractical to attempt to discuss all of 
the operations that the milling machine can do. 
We will limit these machining operations to plain, 
face, and angular milling; milling flat surfaces on 
cylindrical work, slotting, parting, and milling 
keyseats and flutes; and drilling, reaming, and 
boring. Even though we will discuss only the more 
common operations, you will find that by using 
a combination of operations, you will be able to 
produce a variety of work projects. We will 
conclude the chapter by discussing the milling 
machine attachments and gearing and gear 
cutting. 

PLAIN MILLING 

Plain milling is the process of milling a flat 
surface in a plane parallel to the cutter axis. You 
get the work to its required size by individually 
milb'ng each of the flat surfaces on the workpiece. 
Plain milling cutters, such as the ones shown in 
figure 11-22, are used for plain milling. If 
possible, select a cutter that is slightly wider than 
the width of the surface to be milled. Make the 
work setup before you mount the cutter. This 
precaution will keep you from accidentally 
striking the cutter and cutting your hands as you 
set up the work. You can mount the work in a 
vise or fixture, or clamp it directly to the milling 
machine table. You can use the same methods that 
you used to hold work in a shaper to hold work 
in a milling machine. Clamp the work as closely 
as possible to the milling machine column so that 
you can mount the cutter near the column. The 
closer you place the cutter and the work to the 
column, the more rigid the setup will be. 

The following steps explain how to machine 
a rectangular work blank (for example, a spacer 
for an engine test stand). 

1 . Mount the vise on the table and position 
the vise jaws parallel to the table length. 



NOTE: The graduations on the vise are 
accurate enough because we are concerned only 
with machining a surface in a horizontal plane. 

2. Place the work in the vise, as shown in 
figure 11-55. 

3. Select the proper milling cutter and arbor. 

4. Wipe off the tapered shank of the arbor 
and the tapered hole in the spindle with a clean 
cloth. 

5. Mount the arbor in the spindle. 

6. Clean and position the spacing collars and 
place them on the arbor so that the cutter is above 
the work. 

7. Wipe off the milling cutter and any 
additional spacing collars that may be needed. 
Then place the cutter, the spacers, and the arbor 
bearing on the arbor, with the cutter keyseat 
aligned over the key. Locate the bearing as closely 
as possible to the cutter. Make sure that the work 
and the vise will clear all parts of the machine. 

8. Install the arbor nut and tighten it finger 
tight only. 

9. Position the overarm and mount the ar- 
bor support. 

10. After supporting the arbor, tighten the 
arbor nut with a wrench. 




C PARALLELS D 

Figure 11-55. Machining sequence to square a block. 



11-32 



11. Set the spindle directional control lever to 
give the required direction of cutter rotation. 

12. Determine the required speed and feed, 
and set the spindle speed and feed controls. 

13. Set the feed trip dogs for the desired 
length of cut and center the work under the cutter. 

14. Lock the saddle. 



15. Engage the spindle clutch and pick up the 



cut. 



16. Pick up the surface of the work by holding 
a long strip of paper between the rotating cutter 
and the work; very slowly move the work toward 
the cutter until the paper strip is pulled between 
the cutter and the work. BE CAREFUL! Keep 
your fingers away from the cutter. A rotating 
milling cutter is very dangerous. 

17. Move the work longitudinally away from 
the cutter and set the vertical feed graduated 
collar at ZERO. 

18. Compute the depth of the roughing cut 
and raise the knee this distance. 

19. Lock the knee, and direct the coolant flow 
on the work and the outgoing side of the cutter. 

20. Position the cutter to within 1/16 inch of 
the work, using hand table feed. 

21 . After completing the cut, stop the spindle. 

22. Return the work to its starting point on 
the other side of the cutter. 

23. Raise the table the distance required for 
the finish cut. 

24. Set the finishing speed and feed, and take 
the finish cut. 

25. When you have completed the operation, 
stop the spindle and return the work to the 
opposite side of the cutter. 

26. Deburr the work and remove it form the 

vise. 

To machine the second side, plate the work 
in the vise as shown in figure 1 1-55B. Rough and 



finish machine side 2, using the same procedures 
that you used for side 1. When you have 
completed side 2, deburr the surface and remove 
the work from the vise. 

Place the work in the vise, as shown in figure 
11-55C with side 3 up. Then rough machine side 
3. Finish machine side 3 for a short distance, 
disengage the spindle and feed, and return the 
work to the starting point, clear of the cutter. Now 
you can safely measure the distance between sides 
2 and 3. If this distance is correct, you can 
continue the cut with the same setting. If it is not, 
adjust the depth of cut as necessary. If the trial 
finishing cut is not deep enough, raise the work 
slightly and take another trial cut. If the trial cut 
is too deep, you will have to remove the backlash 
from the vertical feed before taking the new depth 
of cut. To remove the backlash: 

1 . Lower the knee well past the original depth 
of the roughing cut. 

2. Raise the knee the correct distance for the 
finishing cut. 

3. Engage the feed. 

4. Stop the spindle. 

5. Return the work to the starting point on 
the other side of the cutter. 

6. Deburr the work. 

7. Remove the work from the vise. 

Place side 4 in the vise, as shown in figure 
11-55D and machine the side, using the same 
procedure as for side 3. When you have completed 
side 4, remove the work from the vise and check 
it for accuracy. 

This completes the machining of the four sides 
of the block. If the block is not too long, you can 
rough and finish mill the ends to size in the same 
manner in which you milled the sides. Do this by 
placing the block on end in the vise. Another 
method of machining the ends is by face milling. 



FACE MILLING 

Face milling is the milling of surfaces that 
are perpendicular to the cutter axis, as shown in 



figure 1 1-56. You do face milling to produce flat 
surfaces and to machine work to the required 
length. In face milling, the feed can be either 
horizontal or vertical. 

Cutter Setup 

You can use straight-shank or taper-shank end 
mills, shell end mills, or face milling cutters for 
face milling. Select a cutter that is slightly larger 
in diameter than the thickness of the material that 
you are machining. If the cutter is smaller in 
diameter than the thickness of the material, you 
will be forced to make a series of slightly over- 
lapping cuts to machine the entire surface. Mount 
the arbor and the cutter before you make the work 
setup. Mount the cutter by any means suitable for 
the cutter you have selected. 

Work Setup 

Use any suitable means to hold the work for 
face milling as long as the cutter clears the 
workholding device and the milling machine 
table. You can mount the work on parallels, if 



necessary, to provide clearance between the cutter 
and the table. Feed the work from the side of the 
cutter that will cause the cutter thrust to force 
the work down. If you hold the work in a vise, 
position the vise so that the cutter thrust is toward 
the solid jaw. The ends of the work are usually 
machined square to the sides of the work. 
Therefore, you will have to align the work 
properly. If you use a vise to hold the work, you 
can align the stationary vise jaw with a dial 
indicator, as shown in figure 1 1-57. You can also 
use a machinist's square and a feeler gauge, as 
shown in figure 11-58. 

Operation 

To face mill the ends of work, such as the 
engine mounting block that we discussed 
previously: 

1. Select and mount a suitable cutter. 

2. Mount and position a vise on the milling 
machine table, as shown in figure 11-56 so the 
thrust of the cutter is toward the solid vise jaw. 




28.402 



COLUMN 




SOLID JAW 
Figure 11-57. Aligning vise jaws using an indicator. 

3. Align the solid vise jaw square with the 
column of the machine, using a dial indicator for 
accuracy. 

4. Mount the work in the vise, allowing the 
end of the work to extend slightly beyond the vise 
jaws. 



5 . Raise the knee until the center of the work 
is approximately even with the center of the cutter. 

6. Lock the knee in position. 

7. Set the machine for the proper roughing 
speed, feed, and table travel. 

8. Start the spindle and pick up the end 
surface of the work by hand feeding the work 
toward the cutter. 

9. Place a strip of paper between the cutter 
and the work as shown in figure 1 1-59 to help pick 
up the surface. When the cutter picks up the 
paper there is approximately .003-inch clearance 
between the cutter and the material being cut. 



VISE 




Figure 11-59. Picking up the work surface. 




-1 <f .f jCO A IStfVMIMSY T*OA IfWWKrO IttCTIMtfV 



10. Once the surface is picked up, set the 
saddle feed graduated dial at ZERO. 

1 1 . Move the work away from the cutter with 
the table and direct the coolant flow onto the 
cutter. 

12. Set the roughing depth of cut, using the 
graduated dial, and lock the saddle. 

1 3 . Position the work to about 1/16 inch from 
the cutter, then engage the power feed. 

14. After completing the cut, stop the spin- 
dle, and move the work back to the starting point 
before the next cut. 

15. Set the speed and feed for the finishing 
cut, and then unlock the saddle. 

16. Move the saddle in for the final depth of 
cut and relock it. 

17. Engage the spindle and take the finish cut. 

18. Stop the machine and return the work to 
the starting place. 

19. Shut the machine off. 

20. Remove the work form the vise. Handle 
it very carefully to keep from cutting yourself 
before you can deburr the work. 

21. Next, mount the work in the vise so the 
other end is ready for machining. Mill this end 
in the same manner as the first, but be sure to 
measure the length before taking the finishing cut. 
Before removing the work from the vise, check 
it for accuracy and remove the burrs from the 
newly finished end. 



ANGULAR MILLING 

Angular milling is the milling of a flat surface 
that is at an angle to the axis of the cutter. You 
can use an angular milling cutter, as shown in 
figure 11-60. However, you can perform angular 
milling with a plain, side, or face milling cutter 
by positioning the work at the required angle. 

Many maintenance or repair tasks involve 
machining flat surfaces on cylindrical work. These 
tasks include milling squares and hexagons, and 
milling two flats in the same plane. 



HORIZONTAL SPINDLE 

SINGLE ANGULAR 
CUTTER 



DOUBLE 
ANGULAR CUTTER 




53-483 



Figure 11-60. Angular milling. 



A square or hexagon is milled on an object 
to provide a positive drive, no slip area for various 
tools, such as wrenches and cranks. You will 
machine squares and hexagons frequently on the 
ends of bolts, taps, reamers, or other items that 
are turned by a wrench and on drive shafts and 
other items that require a positive drive. The 
following information will help you to understand 
the machining of squares and hexagons. 

Cutter Setup 

The two types of cutters you will use most 
often to machine squares or hexagons are side and 
end milling cutters. You can use side milling 
cutters for machining work that is held in a chuck 
and for heavy cutting. You can use end mills for 
work that is held in a chuck or between centers 
and for light cutting. If you use a side milling 
cutter, be sure the cutter diameter is large enough 
so you can machine the full length of the square 
or hexagon without interference from the arbor. 
If you use an end mill, be sure it is slightly larger 
in diameter than the length of the square or 
hexagon. The cutter thrust for both types should 
be up when the work is mounted vertically and 
down when it is mounted horizontally in order 
to use conventional (or up) milling. 

The reason for what appears to be a contra- 
diction in the direction of thrust is the difference 
in the direction of the feed. You can see this by 
comparing figures 11-61 and 11-62. The cutter 




Figure 11-61. Milling a square on work held vertically. 



28.407 




Figure 11-62. Milling a square on work held horizontally. 



shown in figure 11-61 rotates in a counterclock- 
wise direction and the work is fed toward the left. 
The cutter shown in figure 11-62 rotates in a 
clockwise direction and the work is fed upward. 

Work Setup 

We have already discussed the methods that 
you will usually use to mount the work. 
Regardless of the workholding method that you 
use, you must align the index spindle in either 
the vertical or the horizontal plane. If you are 
machining work between centers, you must also 
align the footstock center. If you use a screw-on 
chuck, take into consideration the cutter rotary 
thrust applied to the work. Always cut on the side 



11-37 



D CUTTER DIAMETER 
I LENGTH OF SQUARE 




A. LOCK SCREW FOR DOG 

B. DRIVE PLATE 

C. TAP 



D. END MILL 

E. TAP SQUARE 

F. FOOTSTOCK 



G. INDEX HEAD 



Figure 11-63. Milling a square using an end mill. 




Figure 11-64. Diagram of a square. 



of the work that will tend to tighten the chuck 
on the index head spindle. When you mount work 
between centers, a dog rotates the work. The drive 
plate, shown in figure 11-63, contains two lock 
screws. One lock screw clamps the drive plate to 
the index center and ensures that the drive plate 



moves with the index spindle. The other lock 
screw clamps the tail of the dog against the side 
of the drive plate slot as shown in figure 1 1-63A. 
This eliminates any movement of the work during 
the machining operation. It may be necessary, 
especially if you are using a short end mill, to 
position the index head (fig. 11-63G) near the 
cutter edge of the table to ensure the cutter and 
the work make contact. 



Calculations 

The following information will help you 
determine the amount of material you must 
remove to produce a square or a hexagon. The 
dimensions of the largest square or hexagon that 
you can machine from a piece of stock must be 
calculated. 

The size of a square (H in fig. 11-64) is 
measured across the flats. The largest square that 
you can cut from a given size of round stock 
equals the diameter of the stock in inches 



11-38 



Opposite side = Side of a square 
Hypotenuse = Diagonal of square 
45 =90 bisected 

^ -,-, Opposite side 
H = 0x0.707 or ^ y P potenuse - sine 45 

The diagonal of a square equals the distance 
across the flats times 1.414. This is expressed as 

G = H x 1.414 or Hypotenuse _ 
Opposite side 

The amount of material that you must remove 
to machine each side of the square is equal to one- 
half the difference between the diameter of the 
stock and the distance across the flats. 



1 = 



G - H 



You use the same formula 
G - 



(1 = 

z- 

to determine the amount of material to remove 
when you are machining a hexagon. 

The size of the largest hexagon that you can 
machine from a given size of round stock (H in 
figure 1 1-65) is equal to the diagonal (the diameter 
of the stock) of the hexagon times 0.866 or 

Opposite side = Largest hexagon that can be' machined 
Hypotenuse = Diagonal or diameter of round stock 



The diagonal of a hexagon equals the distance 
across the flats times 1.155, or 



The length of a flat is equal to one-half the 
length of the diagonal, 




r 2 



Figure 11-65. Diagram of a hexagon. 



We will explain two methods of machining a 
square or hexagon: machining work mounted in 
a chuck and machining work mounted between 
centers. 

You can machine a square or hexagon on 
work mounted in a chuck by using either a side 
milling cutter or an end mill. We will discuss using 
the side milling cutter first. Before placing the 
index head on the milling machine table, be sure 
that the table and the bottom of the index head 
have been cleaned of all chips and other foreign 
matter. Spread a thin film of clean machine oil 
over the area of the table to which the index head 
will be attached to prevent corrosion. 

NOTE: Because most index heads are quite 
heavy and awkward, you should get someone to 
help you place the head on the milling machine 
table. 

After you have mounted the index head on the 
table, position the head spindle in the vertical 
position, as shown in figure 1 1-61 . Use the degree 
graduations on the swivel block. This is accurate 
enough for most work requiring the use of the 
index head. The vertical position will allow you 
to feed the work horizontally. 

Then, tighten the work in the chuck to keep 
it from turning due to the cutter's thrust. Install 
the arbor, cutter, and arbor support. The cutter 
should be as close as practical to the column. 
Remember, this is done so the setup will be more 
rigid. Set the machine for the correct roughing 
speed and feed. 

1 . With the cutter turning, pick up the cut on 
the end of the work. 



11-39 



2. Move the work sideways to clear the 
cutter. 

3. Raise the knee a distance equal to the 
length of the flat surfaces to be cut. 

4. Move the table toward the revolving cutter 
and pick up the side of the work. Use a piece of 
paper in the same manner as discussed earlier in 
this chapter. 

5 . Set the crossfeed graduated dial at ZERO. 

6. Move the work clear of the cutter. 
Remember, the cutter should rotate so that the 
cutting action takes place as in "up milling.*' 

7 . Feed the table in the required amount for 
a roughing cut. 

8. Engage the power feed and the coolant 
flow. 

9. When the cut is finished, stop the spin- 
dle and return the work to the starting point. 

10. Loosen the index head spindle lock. 

1 1 . Rotate the work one-half revolution with 
the index crank. 

12. Tighten the index head spindle lock. 

13. Take another cut on the work. 

14. When this cut is finished, stop the cutter 
and return the work to the starting point. 

15. Measure the distance across the flats to 
determine whether the cutter is removing the same 
amount of metal from both sides of the work. If 
not, check your calculations and the setup for a 
possible mistake. 

16. If the work measures as it should, loosen 
the index head spindle lock and rotate the work 
one-quarter revolution, tighten the lock, and take 
another cut. 

17. Return the work to the starting point 
again. 

18. Loosen the spindle lock. 

19. Rotate the work one-half revolution. 

20. Take the fourth cut. 

21 . Return the work again to the starting point 
and set the machine for finishing speed and feed. 

22. Now, finish machine opposite sides 
(1 and 3), using the same procedures already 
mentioned. 

23. Check the distance across these sides. If 
it is correct, finish machine the two remaining 
sides. 

24. Deburr the work and check it for 
accuracy. 

NOTE: You can also machine a square or 
hexagon with the index head spindle in the 
horizontal position, as shown in figures 1 1-62 and 
11-63. If you use the horizontal setup, you must 
feed the work vertically. 



Square or Hexagon Work 
Mounted Between Centers 

Machining a square or hexagon on work 
mounted between centers is done in much the 
same manner as when the work is held in a chuck. 

1 . Mount the index head the same way, only 
with the spindle in a horizontal position. The feed 
will be in a vertical direction. 

2. Insert a center into the spindle and align 
it with the footstock center. 

3. Select and mount the desired end mill, 
preferably one whose diameter is slightly greater 
than the length of the flat you are to cut, as shown 
in figure 11-63. 

4. Mount the work between centers. Make 
sure that the drive dog is holding the work 
securely. 

5. Set the machine for roughing speed and 
feed. 

6. Pick up the side of the work and set the 
graduated crossfeed dial at ZERO. 

7. Lower the work until the cutter clears the 
footstock. 

8. Move the work until the end of the work 
is clear of the cutter. 

9. Align the cutter with the end of the work. 
Use a square head and rule, as shown in figure 
11-66. 

NOTE: Turn the machine off before aligning 
the cutter by this method. 




SQUARE HEAD 



Figure 11-66. Aligning the work and the cutter. 



12. While feeding the work vertically, 
machine side 1. Lower the work to below the 
cutter when you have completed the cut. 

13. Loosen the index head spindle lock and 
index the work one-half revolution to machine the 
fiat opposite side 1. 

14. Tighten the lock. 

15. Engage the power feed. After completing 
the cut, again lower the work to below the cutter 
and stop the cutter. 

16. Measure the distance across the two flats 
to check the accuracy of the cuts. If it is correct, 
index the work one-quarter revolution to machine 
another side. Then lower the work, index one-half 
revolution, and machine the last side. Remember 
to lower the work to below the cutter again. 

17. Set the machine for finishing speed, feeds, 
and depth of cut, and finish machine all the sides. 

18. Deburr the work and check it for 
accuracy. 



Machining Two Flats in One Plane 

Ybu will often machine flats on shafts to serve 
as seats for setscrews. One flat is simple to 
machine. You can machine in in any manner with 
a side or end mill, as long as you can mount the 
work properly. However, machining two flats in 
one plane, such as the flats on the ends of a 
mandrel, presents a problem since the flats must 
align with each other. A simple method of 
machining the flats is to mount the work in a vise 
or on V-blocks in such a manner that you can 
machine both ends without moving the work once 
it has been secured. 

We will describe the method that is used when 
the size or shape of the work requires reposition- 
ing it to machine both flats. 

1 . Apply layout dye to both ends of the work. 

2. Place the work on a pair of V-blocks, as 
shown in figure 11-67. 

3. Set the scriber point of the surface gauge 
to the center height of the work. Scribe horizontal 
lines on both ends of the work, as illustrated in 
figure 11-67. 

4. Mount the index head on the table with its 
spindle in the horizontal position. 

5. Again, set the surface gauge scriber point, 
but to the centerline of the index head spindle. 



SCRIBED LINE 




SURFACE 6UAGE 



Figure 11-67. Layout of the work. 



6. Insert the work in the index head chuck 
with the end of the work extended far enough to 
permit all required machining operations. 

7. To align the surface gauge scriber point 
with the scribed horizontal line, rotate the index 
head spindle. 

8. Lock the index head spindle in position. 

These flats can be milled with either an end 
mill or a side mill or a side milling cutter. 



CAUTION 

Rotate the cutter in a direction that will 
cause the thrust to tighten the index head 
chuck on the spindle when you use a screw- 
on type chuck. 

9. Raise the knee with the surface gauge still 
set at center height until the cutter centerline is 
aligned with the scriber point. This puts the 
centerlines of the cutter and the work in align- 
ment with each other. 

10. Position the work so that a portion of the 
flat to be machined is located next to the cutter. 
Because of the shallow depth of cut, compute the 
speed and feed as if the cuts were finishing cuts. 

1 1 . After starting the machine, feed the work 
by hand so the cutter contacts the side of the work 
on which the line is scribed. 



11-41 



12. Move the work clear of the cutter and stop 
the spindle. 

13 . Check to see if the greater portion of the 
cutter mark is above or below the layout line. 
Depending on its location, rotate the index head 
spindle as required to center the mark on the 
layout line. 

14. Once the mark is centered, take light "cut 
and try" depth of cuts until you reach the desired 
width of the flat. 

15. Machine the flat to the required length. 

16. When one end is completed, remove the 
work from the chuck. Turn the work end for end 
and reinsert it in the chuck. 

17. Machine the second flat in the same 
manner as you did the first. 

18. Deburr the work and check it for 
accuracy. 

19. Check the flats to see if they are in the 
same plane by placing a matched pair of parallels 
on a surface plate and one flat on each of the 
parallels. If the flats are in the same plane, you 
will not be able to wobble the work. 



SLOTTING, PARTING, AND MILLING 
KEYSEATS AND FLUTES 

Slotting, parting, and milling key seats and 
flutes are all operations that involve cutting 
grooves in the work. These grooves are of various 
shapes, lengths, and depths, depending on the 
requirements of the job. They range from flutes 
in a reamer to a keyseat in a shaft, to the parting 
off of a piece of metal to a predetermined length. 



Slotting 

You can cut internal contours, such as internal 
gears and splines and six- or twelve-point sockets 
by slotting. Most slotting is done with a milling 
machine attachment called a slotting attachment, 
as shown in figure 11-68. The slotting attachment 
is fastened to the milling machine column and 
driven by the spindle. This attachment changes 
the rotary motion of the spindle to a reciprocating 
motion much like that of a shaper. You can vary 
the length of the stroke within a specified range. 
A pointer on the slotting attachment slide 
indicates the length of the stroke. You can pivot 
the head of the slotting attachment and position 
it at any desired angle. Graduations on the base 
of the slotting attachment indicate the angle at 
which the head is positioned. The number of 



MACHINE COLUMN 



GRADUATIONS 




SLOTTING ATTACHMENT 

* 
.-- 

SLOTTING TOOL 



Figure 11-68. Slotting attachment. 



strokes per minute is equal to the spindle rpm and 
is determined by the formula: 



Strokes per minute = 



CFSx4 



length of stroke 



The cutting tools used with slotting attach- 
ments are ground to any desired shape from high- 
speed steel tool blanks and are clamped to the 
front of the slide or ram. You can use any suitable 
means for holding the work, but the most 
common method is to hold the work in an index 
head chuck. If the slotted portion does not 
extend through the work, you will have to 
machine an internal recess in the work to provide 
clearance for the tool runout. When it is possible, 
position the slotting attachment and the work in 
the vertical position to provide the best possible 
view of the cutting action of the tool. 

Parting 

Use a metal slitting saw for sawing or parting 
operations and for milling deep slots in metals and 
in a variety of other materials. Efficient sawing 
depends to a large extent on the slitting saw you 
select. The work required of slitting saws varies 
greatly. It would not be efficient to use the same 
saw to cut very deep narrow slots, part thick 
stock, saw thin stock, or saw hard alloy steel. Soft 
metals, such as copper and babbitt, or nonmetallic 
materials, such as bakelite, fiber, or plastic, 
require their own style of slitting saw. 



Parting with a slitting saw leaves pieces that 
are reasonably square and that require the 
removal of a minimum of stock in finishing the 
surface. You can cut off a number of pieces of 
varying lengths and with less waste of material 
than you could saw by hand. 

A coarse-tooth slitting saw is best for sawing 
brass and for cutting deep slots. A fine-tooth 
slitting saw is best for sawing thin metal, and a 
staggered-tooth slitting saw is best for making 
heavy deep cuts in steel. You should use slower 
feeds and speeds to saw steels to prevent cutter 
breakage. Use conventional milling in sawing 
thick material. In sawing thin material, however, 
clamp the stock directly to the table and use down 
milling. Then the slitting saw will tend to force 
the stock down on the table. Position the work 
so the slitting saw extends through the stock and 
into a table T-slot. 

External Keyseat 

Machining an external keyseat on a milling 
machine is less complicated than machining it on a 
shaper. In milling, starting an external keyseat is no 
problem. You simply bring the work into contact 
with a rotating cutter and start cutting. It should 
not be difficult for you to picture in your mind 
how you would mill a straight external keyseat with 
a plain milling cutter or an end mill. If the speci- 
fied length of the keyseat exceeds the length you 
can obtain by milling to the desired depth, you 
can move the work in the direction of the slot to 
obtain the desired length. Picturing in your mind 
how you would mill a Woodruff keyseat should 
be easier. The secret is to select a cutter that has 
the same diameter and thickness as the key. 



CUTTER 



THIN PAPER 




Straight External Keyseats 

Normally, you would use a plain milling 
cutter to mill a straight external keyseat. You 
could use a Woodruff cutter or a two-lipped end 
mill. 

Before you can begin milling the keyseat, you 
must align the axis of the work with the midpoint 
of the width of the cutter. Figure 1 1-69 shows one 
method of alignment. 

Suppose that you are going to cut a keyseat 
with a plain milling cutter. Move the work until 
the side of the cutter is tangent to the 
circumference of the work. With the cutter 
turning very slowly and before contact is made, 
insert a piece of paper between the work and the 
side of the cutter. Continue moving the work 
toward the cutter until the paper begins to tear. 
When it does, lock the graduated dial at ZERO 
on the saddle feed screw. Then lower the milling 
machine knee. Use the saddle feed dial as a guide, 
and move the work a distance equal to the radius 
of the work plus one-half the width of the cutter 
to center the cutter over the centerline of the 
keyseat to be cut. 

You use a similar method to align work with 
an end mill. When you use an end mill, move the 
work toward the cutter while you hold a piece of 
paper between the rotating cutter and the work, 
as shown in figure 11-70. After the paper tears, 
lower the work to just below the bottom of the 



PAPER 



V-BLOCK 




Figure 11-69. Aligning the cutter using a paper strip. 



Figure 11-70. Aligning an end mill with the work. 



RULE 




Figure 11-71. Visual alignment of a cutter. 



end mill. Then move the work a distance equal 
to the radius of the work plus the radius 
of the end mill to center the mill over the 
centerline of the keyseat to be cut. Move 
the work up, using hand feed, until a piece 



of paper held between the work and the 
bottom of the end mill begins to tear, as 
shown in figure 11-70B. Then move the table 
and work away from the bottom of the end mill. 
Set and lock the graduated dial at ZERO on the 
vertical feed, and then feed up for the roughing 
cut. You can determine the cutter rpm and the 
longitudinal feed in the same manner as you do 
for conventional milling cutters. Because of the 
higher speeds and feeds involved, more heat is 
generated, so flood the work and the cutter with 
coolant. 

When extreme accuracy is not required, you 
can align the work with the cutter visually, as 
shown in figure 11-71. Position by eye the work 
as near as possible to the midpoint of the cutter. 
Make the final alignment by moving the work in 
or out a slight amount, as needed. The cutter 
should be at the exact center of the work diameter 
measurement of the steel rule. You can use this 



Table 11-1. -Values for Factor (f) for Various Sizes of Shafts 



WIDTH OF KEY IN INCHES 


DIAMETER 
OF SHAFT 
(INCHES) 


1/16 


3/32 


1/8 


5/32 


3/16 


7/32 


1/4 


5/16 



SHAFT SIZE 


FACTOR (f) 


1/2 


. 002 


. 004 


. 008 


. 013 


. 018 


. 025 


. 033 


... 


5/8 


. 001 


. 003 


. 006 


. 010 


. 014 


. 019 


. 025 


. 042 


3/4 


. 001 


. 003 


. 005 


. 008 


. 012 


. 016 


. 022 


. 034 


7/8 


. 001 


. 002 


. 004 


. 007 


. 010 


. 014 


. 018 


. 028 


1 


. 001 


. 002 


. 004 


. 006 


. 009 


. 012 


. 015 


. 024 


1 1/8 





. 002 


. 003 


. 005 


. 008 


. Oil 


. 014 


. 022 


1 1/4 





. 002 


. 003 


. 005 


. 007 


. 010 


. 013 


. 019 


1 1/2 





. 001 


. 002 


. 004 


. 006 


. 008 


.011 


. 016 


1 3/4 





. 001 


. 002 


. 003 


. 005 


. 007 


. 009 


. 014 




square key seat by using the following formula 
based on dimensions shown in figure 11-72. 



Figure 11-72. Keyseat dimensions for a straight square key. 



method with both plain milling cutters and end 
mills. 

Before you begin to machine the keyseat, you 
should measure the width of the cut. You cannot 
be certain that the width will be the same as the 
thickness of the cutter. The cutter may not run 
exactly true on the arbor or the arbor may not 
run exactly true on the spindle. The recommended 
practice is to nick the end of the work with the 
cutter and then to measure the width of the cut. 

Specifications for the depth of cut are usually 
furnished. When specifications are not available, 
you can determine the total depth of cut for a 



where 



Total depth of cut (T) = d + f 



W 



d = -5- = depth of the keyseat 



f = R - VR 2 - (y) = height of arc 

W = width of the key 
R = radius of the shaft 

The height of arc (f) for various sizes of 
shafts and keys is shown in table 11-1. Keyseat 
dimensions for rounded end and rectangular keys 
are contained in the Machinery's Handbook. 
Check the keyseats for accuracy with rules, out- 
side and depth micrometers, vernier calipers, and 
go-no-go gauges. Use table 11-1 for both square 
and Woodruff keyseats, which will be explained 
next. 

Woodruff Keyseat 

A Woodruff key is a small half-disk of metal. 
The rounded portion of the key fits in the slot in 
the shaft. The upper portion fits into a slot in a 
mating part, such as a pulley or gear. You align 
the work with the cutter and measure the width 
of the cut in exactly the same manner as you do 
for milling straight external keyseats. 

A Woodruff keyseat cutter (fig. 11-73) has 
deep flutes cut across the cylindrical surface of 





Figure 11-73. Woodruff keyseat cutter. 




28.416 



Figure 11-74. Milling a Woodruff keyseat. 





Figure 11-75. Dimensions for a Woodruff keyseat. 



of the teeth than it is at the center. This feature 
provides clearance between the sides of the slot 
and the cutter. Cutters with a 2-inch diameter 
and larger have a hole in the center for arbor 
mounting. On smaller cutters the cutter and the 
shank are one piece. Note that the shank is 
"necked" in back of the cutting head to give 
additional clearance. Also, note that large cutters 
usually have staggered teeth to improve their 
cutting action. 

As discussed earlier, to mill a Woodruff 
keyseat in a shaft, you use a cutter that has the 
same diameter and thickness as the key. Cutting 
a Woodruff keyseat is relatively simple. You 
simply move the work up into the cutter until you 
obtain the desired keyseat depth. The work may 
be held in a vise, chuck, between centers, or 
clamped to the milling machine table. The cutter 
is held on an arbor, or in a spring collet or drill 
chuck that has been mounted in the spindle of the 
milling machine, as in figure 11-74. 

In milling the keyseat, centrally locate the 
cutter over the position in which the keyseat is 
to be cut and parallel with the axis of the work. 
Raise the work by using the hand vertical feed 
until the revolving cutter tears a piece of paper 
held between the teeth of the cutter and the work. 
At this point, set the graduated dial on the 
vertical feed at ZERO and set the clamp on the 
table. With the graduated dial as a guide, raise 
the work by hand until the full depth of the 
keyseat is cut. If specifications for the total depth 
of cut are not available, use the following formula 
to determine the correct value: 



Total depth (T) = d + f 



where 



W 



d (depth of the keyseat) = H - 

^ 

H = total height of the key 
W = width of the key 

The most accurate way to check the depth of 
a Woodruff keyseat is to insert a Woodruff key 
of the correct size in the keyseat. Measure over 
the key and the work with an outside micrometer 
to obtain the distance M in figure 1 1-75. Measure 
the correct micrometer reading over the shaft and 



using the formula 

\* ^ , (W) f 

(2) ~ 

where 

M = micrometer reading 
D = diameter of the shaft 
W = width of the key 

f = height of the arc between the top of 
the slot and the top of the shaft. 

NOTE: Tables in some references may differ 
slightly from the above calculation for the value 
M, due to greater allowance for clearance at the 
top of the key. 

Straight Flutes 

The flutes on cutting tools serve three 
purposes. They form the cutting edge for the tool, 
provide channels for receiving and discharging 
chips, and let coolant reach the cutting edges. The 
shape of the flute and the tooth depends on the 
cutter you use to machine the flute. The following 
information pertains specifically to taps and 
reamers. Since flutes are actually special purpose 
grooves, you can apply much of the information 
to grooves in general. 

Tap Flutes 

You usually use a convex cutter to machine 
tap flutes. This type of cutter produces a 
"hooked" flute as shown in figure 11-76. The 



CONVEX CUTTER 




CUTTER WIDTH 1/2 
TAP DIAMETER 



HOOKED PLAJTE 



-DEPTH OF FLUTE 
1/6 TAP DIAMETER 



Figure 11-76. Hooked tap flutes. 



11-47 



number of flutes is determined by the diameter 
of the tap. Taps 1/45 inch to 1 3/4 inches in 
diameter usually have four flutes, and taps 1 7/8 
inches (and larger) in diameter usually have six 
flutes. The width of the convex cutter should be 
equal to one-half the tap diameter. The depth of 
the flute is normally one-fourth the tap diameter. 
The minimum length of the full depth of the flute 
should be equal to the length of the threaded 
portion of the tap. Table 11-2 lists the width of 
the cutter and the depth of the flutes for taps of 
various diameters. You usually mount the tap 
blank between centers and feed it longitudinally 
past the cutter. For appearance sake, the flutes 
are usually cut in the same plane as the sides of 
the square on the tap blank. 



You can mill the flutes on a tap blank in the 
following manner. 

1. Mount and align the index centers. 

2. Set the surface gauge to center height. 

3. Place the tap blank between the centers 
with one flat of the square on the tap shank in 
a vertical position. 

4. Align the flat with a square head and blade. 

5. Scribe a horizontal line on the tap shank. 

6. Remove the tap blank, place a dog on the 
shank, and remount the blank between centers. 

7 . Align the scribed line with the point of the 
surface gauge scriber. 

8. Make sure that the surface gauge is still at 
center height. 



Table 11-2. Tap Flute Dimensions 



Diameter of tap 
(inches) 


Width of cutter 
(inches ) 


Depth of flute 
(inches ) 


1/8 


1/16 


1/32 


1/4 


1/8 


1/16 


1/2 


1/4 


1/8 


3/4 


3/8 


3/16 


1 


1/2 


1/4 


1 1/4 


5/8 


5/16 


1 1/2 


3/4 


3/8 


1 3/4 


7/8 


7/16 


2 


1 


1/2 


2 1/4 


1 1/8 


9/16 


2 1/2 


1 1/4 


5/8 


2 3/4 


1 3/4 


11/16 


3 


1 1/2 


3/4 



Table 11-3. Reamer Fluting Cutter Numbers 



Cutter number 


Reamer diam- 
eter (inches) 


Number of 
reamer flutes 


1 


1/8 to 3/16 


6 


2 


1/4 to 5/16 


6 


3 


3/8 to 7/16 


6 


4 


1/2 to 11/16 


6 to 8 


5 


3/4 to 1 


8 


6 


1 1/16 to 1 1/2 


10 


7 


1 9/16 to 2 1/8 


12 


8 


2 1/4 to 3 


14 



11-48 



9. Mount the convex cutter. 

10. Make sure that the direction of the cutter 
rotation is correct for conventional (or up) milling 
and that the thrust is toward the index head. 

1 1 . Align the center of the cutter with the axis 
of the tap blank. 

12. Pick up the surface of the tap. 

13. Set the table trip dogs for the correct 
length of cut. 

14. Set the machine for roughing speed and 
feed. 

15. Rough mill all flutes to within 0.015 to 
0.020 inch of the correct depth. 

16. Set the machine for finishing speed and 
feed and finish machine all flutes to the correct 
size. 

17. Remove the work, deburr it, and check 
it for accuracy. 

Reamer Flutes 

You may mill flutes on reamers with angular 
fluting cutters, but you normally use special 
formed fluting cutters. The advantages of cutting 
the flutes with a formed cutter rather than with 
an angular cutter are that the chips are more 
readily removed and the flute cutting teeth are 
stronger. Also, the teeth are less likely to crack 
or warp during heat treatment. Formed reamer 
fluting cutters have a 6 angle on one side and 



FORMED REAMER 
CUTTER 



ARBOR 




AMOUNT OF OFFSET 



a radius on the other side. The size of the radius 
depends on the size of the cutter. Reamer fluting 
cutters are manufactured in eight sizes. The 
size of the cutter is identified by a number 
(1 through 8). Reamers from 1/8 inch to 3 inches 
in diameter are fluted by the eight sizes of cutters. 
The correct cutters for fluting reamers of various 
diameters are given in table 11-3. You machine 
reamer teeth with a slight negative rake to help 
prevent chatter. To obtain the negative rake, 
position the work and cutter slightly ahead of the 
reamer center, as shown in figure 11-77. 

Table 11-4 lists the recommended offset for 
reamers of various sizes. Straight reamer flutes 
are usually unequally spaced to help prevent 
chatter. To obtain the unequal spacing, index 
the required amount as each flute is cut. The 
recommended variation is approximately 2. 
Machinists' publications, such as Machinery's 
Handbook, contain charts that list the number of 
holes to advance or retard the index crank to 
machine a given number of flutes when you use 
a given hole circle. You normally mill the flutes 
in pairs. After you have machined one flute, 
index the work one-half revolution and mill the 
opposite flute. 

The depth of the flute is determined by trial 
and error. The approximate depth of flute to 
obtain the recommended width of land is one- 
eighth the diameter for an eight-fluted reamer, 
one-sixth the diameter for a six-fluted reamer, and 
so on. 



Table 11-4. Required Offset 



REAMER 



Size of reamer 
(inches) 


Offset of cutter 
(inches) 


1/4 


0.011 


3/8 


0.016 


1/2 


0.022 


5/8 


0.027 


3/4 


0.033 


7/8 


0.038 


1 


0.044 


1 1/4 


0.055 


1 1/2 


0.066 


1 3/4 


0.076 


2 


0.087 


2 1/4 


0.098 


2 1/2 


0.109 


2 3/4 


0.120 


3 


0.131 



Figure 11-77. Negative rake tooth. 



You can machine the flutes on a hand reamer 
in the following manner: 

1 . Mount the reamer blank between centers 
and the reamer fluting cutter on the arbor. 

2. Align the point of the cutter with the 
reamer blank axis and just touch the surface of 
the reamer with the rotating cutter. 

3. Remove the work blank. 

4. Then raise the table a distance equal to the 
depth of the flute plus one-half the grinding 
allowance. 

5. Rotate the cutter until a tooth is in the 
vertical position. 

6. Shut off the machine. 



7. Move the table until the point of the 
footstock center is aligned with the tooth that is 
in the vertical position. 

8 . Place an edge of a 3 -inch rule against the 
6 surface of the reamer tooth. Move the 
saddle until the edge of the 3 -inch rule that is 
contacting the cutter tooth is aligned with the 
point of the footstock center. 

9. To eliminate backlash, move the saddle 
in the same direction it will be moved when you 
offset the cutter. Continue feeding the saddle until 
you get the desired amount of offset; then lock 
it in position. 

10. Move the table until the cutter clears the 
end of the reamer blank. 

1 1 . Remount the blank between the centers. 




12. Calculate the indexing required to space 
the flutes unequally. 

13. Set the table feed trip dogs so the 
minimum length of the full depth of flute is equal 
to the length of the reamer teeth. 

14. Rough machine all flutes. 

NOTE: Write down the exact indexing which 
you used for each of the flutes to avoid 
confusion when you index for the finish cut. 

Fly Cutting 

You will use a fly cutter when a formed cutter 
is required but is not available. Fly cutters are 
high-speed steel tool blanks that have been ground 
to the required shape. Any shape can be ground 
on the tool if the cutting edges are given a 
sufficient amount of clearance. Fly cutters are 
mounted in fly cutter arbors, such as the one 
shown in figure 11-45. Use a slow feed and a 
shallow depth of cut to prevent breaking the tool. 
It is a good idea to rough out as much excess 
material as possible with ordinary cutters and to 
use the fly cutter to finish shaping the surface. 

DRILLING, REAMING, AND BORING 

Drilling, reaming, and boring are operations 
that you can do very efficiently on a milling 
machine. The graduated feed screws make it 
possible to accurately locate the work in relation 
to the cutting tool. In each operation the cutting 
tool is held and rotated by the spindle, and the 
work is fed into the cutting tool. 



Boring 

Of the three operations, the only one that 
warrants special treatment is boring. On a milling 
machine you usually bore holes with an offset 
boring head. Figure 1 1-78 shows several views of 
an offset boring head and several boring tools. 
Note that the chuck jaws, which grip the boring 
bar, can be adjusted at a right angle to the 
spindle axis. This feature lets you accurately 
position the boring cutter to bore holes of varying 
diameters. This adjustment is more convenient 
than adjusting the cutter in the boring bar holder 
or by changing boring bars. 

Although the boring bars are the same on a 
milling machine as on a lathe or drill press, the 
manner in which they are held is different. Note 
in figure 11-79 that a boring bar holder is not 
used. The boring bar is inserted into an adapter 
and the adapter is fastened in the hole in the 
adjustable slide. Power for driving the boring bar 
is transmitted directly through the shank. The 
elimination of the boring bar holder results in a 
more rigid boring operation, but the size of the 
hole that can be bored is more limited than in 
boring on a lathe or a drill press. 

Fly cutters, which we discussed previously, can 
also be used for boring, as shown in figure 11-79. 
A fly cutter is especially useful for boring 
relatively shallow holes. The cutting tool must be 
adjusted for each depth of cut. 

The speeds and feeds you should use in boring 
on a milling machine are comparable to those you 
would use in boring on a lathe or drill press and 
depend on the same factors: hardness of the 



Drilling and Reaming 

You use the same drills and reamers that you 
use for drilling and reaming in the lathe and the 
drill press. Drills and reamers are held in the 
spindle by the same methods that you use to hold 
straight and taper-shanked end mills. The work 
may be held in a vise, clamped to the table, held 
in fixtures or between centers, and in index head 
chucks, as is done for milling. You determine the 
speeds used for drilling and reaming in the same 
manner as for drilling and reaming in the lathe 
or the drill press. The work is fed into the drill 
or reamer by either hand or power feed. If you 
mount the cutting tool in a horizontal position, 
use the transverse or saddle feed. If you mount 
a drill or reamer in a vertical position, as in a 
vertical type machine, use the vertical feed. 



WORK 




Figure 11-79. Boring with a fly cutter. 



metal, kind of metal in the cutting tool, and depth 
of cut. Because the boring bar is a single-point 
cutting tool, the diameter of the arc through which 
the tool moves is also a factor. For all of these 
reasons you must guard against operating at too 
great a speed, or vibration will occur. 



MILLING MACHINE 
ATTACHMENTS 

Many attachments have been developed that 
increase the number of jobs a milling machine can 
do, or which make such jobs easier to do. 

VERTICAL MILLING ATTACHMENT 

For instance, by using a vertical milling attach- 
ment (fig. 1 1-80) you can convert the horizontal 
spindle machine to a vertical spindle machine and 
can swivel the cutter to any position in the 
vertical plane. By using a universal milling attach- 
ment, you can swivel the cutter to any position 
in both the vertical and horizontal planes. These 
attachments will enable you to more easily do jobs 
that would otherwise be very complex. 

HIGH-SPEED UNIVERSAL 
ATTACHMENT 

By using a high-speed universal attachment, 
you can perform milling operations at higher 
speeds than those for which the machine was 
designed. This attachment is clamped to the 



DRAWBOLT 



DEGREE 
GRADUATIONS 




machine and is driven by the milling machine 
spindle, as you can see in figure 11-81. You can 
swivel the attachment spindle head and cutter 360 
in both planes. The attachment spindle is driven 
at a higher speed than the machine spindle. You 
must consider the ratio between the rpm of the 
two spindles when you calculate cutter speed. 
Small cutters, end mills, and drills should be 
driven at a high rate of speed to maintain an 
efficient cutting action. 

CIRCULAR MILLING ATTACHMENT 

This attachment (fig. 11-82) is a circular table 
that is mounted on the milling machine table. The 
circumference of the table is graduated in degrees. 
Smaller attachments are usually equipped for 
hand feed only, and larger ones are equipped for 
both hand and power feed. This attachment may 
be used for milling circles, arcs, segments, circular 
T-slots, and internal and external gears. It may 
also be used for irregular form milling. 

RACK MILLING ATTACHMENT 

The rack milling attachment, shown in 
figure 11-83, is used primarily for cutting teeth 
on racks, although it can be used for other 
operations. The cutter is mounted on a spindle 
that extends through the attachment parallel to 
the table T-slots. An indexing arrangement is used 
to space the rack teeth quickly and accurately. 



DEGREE GRADUATION 



SPINDLE 




Figure 11-80. Vertical milling attachment. 



Figure 11-81. High-speed universal milling attachment. 



DEGREE GRADUATIONS 



ROTARY TABLE 



DRIVE SHAFT 




HAND WHEEL 

END GEARING HOUSING 

Figure ll-82.-CircuIar milling attachment with power feed. 



Figure ll-83.-Rack milling attachment. 

11-53 



28.423 




28.424X 



RIGHT-ANGLE PLATE 

The right-angle plate (fig. 11-84) is attached 
to the table. The right-angle slot permits mounting 
the index head so the axis of the head is parallel 
to the milling machine spindle. With this attach- 
ment you can make work setups that are off center 
or at a right angle to the table T-slots. The 
standard size plate T-slots make it convenient to 
change from one setting to another for milling a 
surface at a right angle. 

RAISING BLOCK 

Raising blocks (fig. 11-85) are heavy-duty 
parallels that usually come in matched pairs. They 
are mounted on the table, and the index head is 
mounted on the blocks. This arrangement raises 
the index head and makes it possible to swing the 
head through a greater range to mill larger work. 

TOOLMAKER'S KNEE 

The toolmaker's knee (fig. 11-86) is a simple 
but useful attachment for setting up angular work, 
not only for milling but also for shaper, drill press, 
and grinder operations. You mount a toolmaker's 




Figure 11-84. Right-angle plate. 




knee, which may have either a stationary or 
rotatable base, to the table of the milling machine. 
The base of the rotatable type is graduated in 
degrees. This feature enables you to machine 
compound angles. The toolmaker's knee has a 
tilting surface with either a built-in protractor 
head graduated in degrees for setting the table or 
a vernier scale for more accurate settings. 



FEEDS, SPEEDS, AND COOLANTS 

Milling machines usually have a spindle speed 
range from 25 to 2,000 rpm and a feed range from 
1/4 inch to 30 inches per minute (ipm). The feed 
is independent of the spindle speed; thus, a 
workpiece can be fed at any rate available in the 
feed range regardless of the spindle speed being 
used. Some of the factors concerning the selection 
of appropriate feeds and speeds for milling are 
discussed in the following paragraphs. 



TILTING SURFACE 
T-SLOTS 




GRADUATIONS 



BASE 




BASE \-GRADUATIONS 



Figure 11-86. Toolmaker's knees. 



Table 11-5. Surface Cutting Speeds 



Figure 11-85. Raising blocks. 





Carbon steel 


High Speed 




cutters (ft. 


steel cutters 




per min. ) 


(ft. per min. ) 




Rough 


Finish 


Rough 


Finish 


Cast iron: 










Malleable 


60 


75 


90 


100 


Hard 










castings 


10 


12 


15 


20 


Annealed tool 










steel 


25 


35 


40 


50 


Low carbon 










steel 


40 


50 


60 


70 


Brass 


75 


95 


110 


150 


Aluminum 


460 


550 


700 


900 



SPEEDS 

Heat generated by friction between the cutter 
and the work may be regulated by the use of 
proper speed, feed, and cutting coolant. Regula- 
tion of this heat is very important because the 
cutter will be dulled or even made useless by 
overheating. It is almost impossible to provide any 
fixed rules that will govern cutting speeds because 
of varying conditions from job to job. Generally 
speaking, you should select a cutting speed that 
will give the best compromise between maximum 
production and longest life of the cutter. In any 
particular operation, consider the following 
factors in determining the proper cutting speed. 

Hardness of the Material Being Cut: The 
harder and tougher the metal being cut, the 
slower should be the cutting speed. 

Depth of Cut and Desired Finish: The 
amount of friction heat produced is 
directly proportional to the amount of 
material being removed. Finishing cuts, 
therefore, often may be made at a speed 
40% to 80% higher than that used in 
roughing. 



9 Cutter Material: High-speed steel cutters 
may be operated from 50% to 100% faster 
than carbon steel cutters -because high- 
speed steel cutters have better heat resistant 
properties than carbon steel cutters. 

Type of Cutter Teeth: Cutters that have 
undercut teeth cut more freely than those 
that have a radial face; therefore, cutters 
with undercut teeth may run at higher 
speeds. 

Sharpness of the Cutter: A sharp cutter 
may be run at much higher speed than a 
dull cutter. 

Use of Coolant: Sufficient coolant will 
usually cool the cutter so that it will not 
overheat even at relatively high speeds. 

Use the approximate values in table 11-5 as 
a guide when you are selecting the proper cutting 
speed. If you find that the machine, the cutter, 
or the work cannot be suitably operated at 
the suggested speed, make an immediate readjust- 
ment. 

By referring to table 11-6, you can determine 
the cutter revolutions per minute for cutters 



Table 11-6. Cutter Speeds in Revolutions Per Minute 





Surface speed (ft. per min. ) 


Diameter 
of cutter 
(in-) 


25 


30 


35 


40 


50 


55 


60 


70 


75 


80 


90 


100 


120 


140 


160 


180 


200 


Cutter revolutions per minute 




1/4 


382 


458 


535 


611 


764 


851 


917 


1,070 


1,147 


1,222 


1,376 


1,528 


1,834 


2,139 


2,445 


2,750 


3,056 


5/16 


306 


367 


428 


489 


611 


672 


733 


856 


917 


978 


1,100 


1,222 


1,466 


1,711 


1,955 


2,200 


2,444 


3/8 


255 


306 


357 


408 


509 


560 


611 


713 


764 


815 


916 


1,018 


1,222 


1,425 


1,629 


1,832 


2,036 


7/16 


218 


262 


306 


349 


437 


481 


524 


611 


656 


699 


786 


874 


1,049 


1,224 


1,398 


1,573 


1,748 


1/2 


191 


229 


268 


306 


382 


420 


459 


535 


573 


611 


688 


764 


917 


1,070 


1,222 


1,375 


1,528 


5/8 


153 


184 


214 


245 


306 


337 


367 


428 


459 


489 


552 


612 


736 


857 


979 


1,102 


1,224 


3/4 


127 


153 


178 


203 


254 


279 


306 


357 


381 


408 


458 


508 


610 


711 


813 


914 


1,016 


7/8 


109 


131 


153 


175 


219 


241 


262 


306 


329 


349 


392 


438 


526 


613 


701 


788 


876 


1 


95.5 


115 


134 


153 


191 


210 


229 


267 


287 


306 


344 


382 


458 


535 


611 


688 


764 


1 1/4 


76.3 


91.8 


107 


123 


153 


168 


183 


214 


230 


245 


274 


306 


367 


428 


490 


551 


612 


1 1/2 


63.7 


76.3 


89.2 


102 


127 


140 


153 


178 


191 


204 


230 


254 


305 


356 


406 


457 


508 


1 3/4 


54.5 


65.5 


76.4 


87.3 


109 


120 . 


131 


153 


164 


175 


196 


218 


262 


305 


34,9 


392 


436 


2 


47.8 


57.3 


66.9 


76.4 


95.5 


105 


115 


134 


143 


153 


172 


191 


229 


267 


306 


344 


382 


2 1/2 


38.2 


45.8 


53.5 


61.2 


76.3 


84.2 


91.7 


107 


114 


122 


138 


153 


184 


213 


245 


275 


306 


3 


31.8 


38.2 


44.6 


51 


63.7 


69.9 


76.4 


89.1 


95.3 


102 


114 


127 


152 


178 


208 


228 


254 


3 1/2 


27.3 


32.7 


38.2 


44.6 


54.5 


60 


65.5 


76.4 


81.8 


87.4 


98.1 


109 


131 


153 


174 


196 


21CI 


4 


23.9 


28.7 


33.4 


38.2 


47.8 


52.6 


57.3 


66.9 


71.7 


76.4 


86 


95.6 


115 


134 


153 


172 


191 


5 


19.1 


22.9 


26.7 


30.6 


38.2 


42 


45.9 


53.5 


57.3 


61.1 


68.8 


76.4 


91.7 


107 


122 


138 


153 



11-55 



varying in diameter from 1/4 inch to 5 inches. For 
example: You are cutting with a 7/16-inch cutter. 
If a surface speed of 160 feet per minute is 
required, the cutter revolutions per minute will 
be 1,398. 

If the cutter diameter you are using is 
not shown in table 11-6, determine the proper 
revolutions per minute of the cutter by using the 
formula: 

(*\ mm - Cutting speed x 12 
W rpm " 3.1416 x Diameter 

or rpm * 0.26?^ D 



where 



rpm = revolutions per minute of the cutter 

fpm = required surface speed in feed per 
minute 

D = diameter of the cutter in inches 



0.2618 = constant = j^ 

EXAMPLE: What is the spindle speed for a 
1/2-inch cutter running at 45 fpm? 



rpm - 



45 



0.2618 x 0.5 



rpm = 343.7 

To determine cutting speed when you know 
the spindle speed and cutter diameter, use the 
following formula: 



fpm x 12 = rpm x 3.1416 x D 

- 3.1416 x Diameter x rpm 

fpm- - n - : - K- 

fpm = 0.2618 x D x rpm 

EXAMPLE: What is the cutting speed of a 
2 1/4-inch end mill running at 204 rpm? 

fpm = 0.2618 x D x rpm 
rpm = 0.2618 x 2.25 x 204 
fpm= 120.1 



FEEDS 

The rate of feed is the rate of speed at 
which the workpiece travels past the cut. When 
selecting the feed, you should consider the follow- 
ing factors: 

Forces are exerted against the work, the 
cutter, and their holding devices during the 
cutting process. The force exerted varies 
directly with the amount of metal being 
removed and can be regulated by adjusting 
the feed and the depth of cut. The feed and 
depth of cut are, therefore, interrelated, 
and depend on the rigidity and power of 
the machine. Machines are limited by the 
power they can develop to turn the cutter 
and by the amount of vibration they can 
withstand when coarse feeds and deep cuts 
are being used. 

The feed and depth of cut also depend on 
the type of cutter being used. For example, 
deep cuts or coarse feeds should not be 
attempted with a small diameter end mill; 
such an attempt would spring or break the 
cutter. Coarse cutters with strong cutting 
teeth can be fed at a relatively high rate 
of feed because the chips will be washed 
out easily by the cutting lubricant. 

Coarse feeds and deep cuts should not be 
used on a frail piece of work or on work 
mounted in such a way that the holding 
device will spring or bend. 

The desired degree of finish affects the 
amount of feed. When a fast feed is used, 
metal is removed rapidly and the finish will 
not be very smooth. However, a slow feed 
rate and a high cutter speed will produce 
a finer finish. For roughing, it is advisable 
to use a comparatively low speed and a 
coarse feed. More mistakes are made by 
overspeeding the cutter than by 
overfeeding the work. Overspeeding is 
indicated by a squeaking, scraping sound. 
If chattering occurs in the milling machine 
during the cutting process, reduce the 
speed and increase the feed. Excessive 
cutter clearance, poorly supported work, 
or a badly worn machine gear are also 
common causes of chattering. 

One procedure for selecting an appropriate 
feed for a milling operation is to consider the chip 



11-56 



load of each cutter tooth. The chip load is the 
thickness of the chip that a single tooth removes 
from the work as it passes over the surface. For 
example, with a cutter turning at 60 rpm, having 
12 cutting teeth, and a feed rate of 1 ipm, the chip 
load of a single tooth of the cutter will be 0.0014 
inch. A cutter speed increase to 120 rpm reduces 
the chip load to 0.0007 inch; a feed increase to 
2 ipm increases chip load to 0.0028 inch. The 
formula for calculating chip load is: 



Chip load = 



feed rate (ipm) 



cutter speed (rpm) x number 
of teeth in the cutter 



Table 11-7 provides recommended chip loads 
for milling various materials with various types 
of cutters. 

COOLANTS 

The purpose of a cutting coolant is to reduce 
frictional heat and thereby extend the life of the 
cutter's edge. Coolant also lubricates the cutter 
face and flushes away the chips, reducing the 
possibility of damage to the finish. 

If a commercial cutting coolant is not 
available, you can make a good substitute by 
thoroughly mixing 1 ounce of sal soda and 1 quart 



Table 11-7. Recommended Chip Loads 



Material 


Face 
Mills 


Helical 
Mills 


Slotting & 
Side Mills 


End 
Mills 


Form 
Relieved 
Cutters 


Circular 
Saws 


Plastic 


.013 


.010 


.008 


.007' 


.004 


.003 


Magnesium and alloys 
Aluminum and alloys 
Free cutting brasses 
& bronzes 


.022 
.022 

.022 


.018 
.018 

.018 


.013 
.013 

.013 


.011 
.011 

.011 


.007 
.007 

.007 


.005 
.005 

.005 


Medium brasses & 


.014 


.011 


.008 


.007 


.004 


.003 


Hard brasses & 
bronzes 


.009 


.007 


.006 


.005 


.003 


.002 




.013 


.010 


.007 


.006 


.004 


.003 


Cast iron, soft (ISO- 
ISO BH)# 


.016 


.013 


.009 


.008 


.005 


.004 


Cast iron, med. (180- 
220 BH) 


.013 


.010 


.007 


.007 


.004 


.003 


Cast iron, hard (220- 
300 BH) 


.011 


.008 


.006 


.006 


.003 


.003 


Malleable iron ..... 


.012 


.010 


.007 


.006 


.004 


.003 


Cast steel . 


.012 


.010 


.007 


.006 


.004 


.003 


Low carbon steel, 
free mach 


.012 


.010 


.007 


.006 


.004 


.003 


Low carbon steel . . . 
Medium carbon steel 
Alloy steel, annealed 
(180-220 BH) 


.010 
.010 

.008 


.008 
.008 

.007 


.006 
.006 

.005 


.005 
.005 

.004 


.003 
.003 

.003 


.003 
.003 

.002 


Alloy steel, tough 
(220-300 BH) 


.006 


.005 


.004 


.003 


.002 


.002 


Alloy steel, hard 
(300-400 BH) 


.004 


.003 


.003 


.002 


.002 


.001 


Stainless steel, free 
mach 


.010 


.008 


.006 


.005 


.003 


.002 


Stainless steels .... 
Monel metals 


.006 
.008 


.005 
.007 


.004 
.005 


.003 
.004 


.002 
.003 


.002 
.002 

















proportionally. This emulsion is suitable for 
machining most metals. 

In machining aluminum, you should use 
kerosene as a cutting coolant. Machine cast iron 
dry, although you can use a blast of compressed 
air to cool the work and the cutter. If you use 
compressed air, be extremely careful to prevent 
possible injury to personnel and machinery. 

When using a periphery milling cutter, apply 
the coolant to the point at which the tooth leaves 
the work. This will allow the tooth to cool before 
you begin the next cut. Allow the coolant to flow 
freely on the work and cutter. 



The horizontal boring mill is used for many 
kinds of shop work, such as facing, boring, 
drilling, and milling. In horizontal boring mill 



milling machine work; therefore, a detailed 
discussion of these operations will not be 
necessary in this section. 

The horizontal boring mill (fig. 1 1-87) consists 
of four major elements. 

BASE AND COLUMN The base contains 
all the drive mechanisms for the machine and 
provides a platform that has precision ways 
machined lengthwise for the saddle. The column 
provides support for the head and has two rails 
machined the height of the column for full 
vertical travel of the head. 

HEAD The head contains the horizontal 
spindle, the auxiliary spindle, and the mechanism 
for controlling them. The head also provides a 
station for mounting various attachments. The 
spindle feed and spindle hand feed controls are 
contained in the head, along with the quick 



COLUMN \ 



MANUAL SPINDLE 
FEED HANDWHEEL 



SPINDLE 
CLAMP LEVER 



FEED CHANGE 
LEVERS 



BACKREST 



TABLE FEED 
DIRECTIONAL LEVER 




SADDLE 



BED 



SPINDLE SPEED 
CHANGE LEVER 



FEED AND RAPID 
TRAVERSE LEVER 



HEAD FEED 
DIRECTIONAL LEVER 



SADDLE FEED 
DIRECTIONAL LEVER 



28.426 



Figure 11-87. Horizontal boring mill. 



11-58 



SADDLE AND TABLE A large rectangular 
slotted table is mounted on a saddle that can be 
traversed the length of the ways. T-slots are 
machined the entire length of the table for holding 
down work and various attachments, such as 
rotary table angle plates, etc. 

BACKREST OR END SUPPORT The 

backrest is mounted on the back end of the ways. 
It is used to support arbors and boring bars as 
they rotate and travel lengthwise through the 
work, such as in-line boring of a pump casing or 
large bearing. The backrest blocks have an 
antifriction bearing, which the boring bar passes 
through and rotates within. The back rest blocks 
travel vertically with the head. 

The two types of horizontal boring mill usually 
found in Navy machine shops and shore repair 
activities are the table type, used for small work, 
and the floor type, used for large work. The floor 
type is the most common of the two types found 
in shops. You will find this machine well-suited 
for repair work where machining of large irregular 
jobs is commonplace. 

The reference to size of horizontal boring mills 
differs with the manufacturer. Some use spindle 
size. For example, Giddings and Lewis model 
SOOT has a 3 -inch spindle. Other manufacturers 
refer to the largest size boring bar the machine 
will accept. In planning a job, consider both of 
these factors along with the table size and the 
height that the spindle can be raised. Always refer 
to the technical manual for your machine. 

Setting up the work correctly is most 
important. Failure to set the work up properly 
can prove costly in man-hours and material. 
Oftentimes you will find that it is not advisable 
to set up a casting to a rough surface and that 
it will be preferable to set it up to the layout lines, 
since these lines will always be used as a reference. 

It is important that holding clamps used to 
secure a piece of work be tight. If you use braces, 
place them so that they cannot come loose. Fasten 
blocks, stops, and shims securely. If a workpiece 
is not properly secured, there is always the 
possibility of ruining the material or the machine 
and the risk of causing injury to machine shop 
personnel. 

Different jobs to be done on the boring mill 
may require different types of attachments. 
Such attachments include angular milling heads, 



available in a variety of diameters. These boring 
heads prove particularly useful in boring large 
diameter holes and facing large castings. Locally 
made collars may be used also. Stub arbors are 
used to increase desired diameters. 

COMBINATION BORING 
AND FACING HEAD 

The boring and facing head (fig. 1 1-88) is used 
for facing and boring large diameters. This attach- 
ment is mounted and bolted directly to the spindle 
sleeve and has a slide with automatic feed that 
holds the boring or facing tools. (This attachment 
can be fed automatically or positioned manually.) 
Although there are various sizes, each is made and 
used similarly. The heads are balanced to permit 
high-speed operation with the tool slide centered. 
Whenever you use tools off center, be careful to 
counterbalance the head, or use it at lower speeds. 

Generally, the boring and facing head will 
come equipped with several toolholders for single- 
point tools, a right angle arm, a boring bar, and 
a boring bar holder that mounts on the slide. 

To set up and operate the boring and facing 
head: 

1 . Retract the spindle of the machine into the 
sleeve. Engage the spindle ram clamp lever. 




Figure 11-88. Combination boring and facing head. 



11-59 



2. Disengage the overrunning spindle feed 
clutch to prevent inadvertent engagement of the 
spindle power feed while you mount the combina- 
tion head on the machine. (If the slide is centered 
and locked, you may run the spindle through it 
for use in other operations without removing the 
attachment, but be sure to disengage the spindle 
overrunning clutch again before you resume use 
of the slide. 

3. Set the spindle for the speed to be used. 

4. Before you shift the spindle back-gear to 
neutral or make any spindle back-gear change 
when the combination head is mounted on the 
sleeve, rotate the sleeve by jogging it until the 
heavy end of the head is down. This is a safety 
precaution to prevent injury to you or damage to 
the work. Any spindle back-gear change requires 
a momentary shift to neutral, allowing free 
turning of the sleeve. The sleeve may then 
unexpectedly rotate until the heavy end of the 
facing head is down, hitting you or the work. 

5 . Lift the head into position on the machine 
at the sleeve by inserting an eyebolt into the tapped 
hole in the top of the head. 

6. To line up the bolt holes in the sleeve with 
those in the head, jog the spindle into position. 

7. After you have tightened the mounting 
bolts, rotate the feed adjusting arm on the back- 
ing plate until the arm points directly toward the 
front. 

8. Mount the restraining block on the head. 

9. Set the slide manually by inserting the tee- 
handled wrench into the slot in the slide adjusting 
dial and turning the wrench until the slide is 
positioned. The dial is graduated in thousandths 
of an inch with one complete turn equaling a 
0.125-inch movement of the slide. 

After the slide is clamped in place, a spring- 
loaded safety clutch prevents movement of the 
slide or damage to the feed mechanism if the feed 
is inadvertently engaged. You must remember that 
this is not provided to allow continuous opera- 
tion of the head when the slide is clamped and 
the feed is engaged. It is a jamming protection 
only. A distinct and continuous ratcheting of the 
safety clutch warns you to unlock the slide or to 
disengage the feed. Do not confuse this warning 
with the intermittent ratcheting of the feed 
driving clutches as the head rotates. The same 
safety clutch stops the feed at the end of travel 
of the slide, thus preventing jamming of the slide 
or the mechanism through overtravel. 



The slide directional lever is located on the 
backing plate beneath the feed adjusting arm. The 
arrows on the face of the selector indicate which 
way it should be turned for feeding the slide in 
either direction. There are also two positions of 
the selector for disengaging the slide feed. The 
direction of the spindle rotation has no effect on 
the direction of the slide feed. 

The slide feed rate adjusting arm scale is 
graduated in 0.010-inch increments from 0.000 to 
0.050 inch, except that the first two increments 
are each 0.005 inch. Set the feed rate by turning 
the knurled adjusting arm to the desired feed in 
thousandths per revolution. 

When you mount the single point toolholders, 
be sure the tool point is on center or slightly below 
center so the cutting edge has proper clearance 
at the small diameters. The feed mechanism may 
be damaged if you operate the head with the tool 
above center. 

After you mount the facing head, perform the 
machining operation using the instructions found 
in the operator's manual for your boring machine. 

RIGHT ANGLE MILLING 
ATTACHMENT 

The right angle milling attachment is mounted 
over the spindle sleeve and is bolted directly to 
the face of the head. It is driven by a drive dog 
inserted between the attachment and the spindle 
sleeve. This attachment lets you perform milling 
operations at any angle setting through a full 360. 
You can perform boring operations at right angles 
to the spindle axis using either the head or the 
table feed depending on the position of the hole 
to be bored. You may use standard milling 
machine tooling, held in the spindle by a drawbolt 
that extends through the spindle. A right angle 
milling attachment is shown in figure 11-89. 

BORING MILL OPERATIONS 

You should be able to perform drilling, ream- 
ing, and boring operations in a boring mill. In 
addition, you may be required to use a boring mill 
to face valve flanges, bore split bearings, and bore 
pump cylindrical liners. 

Drilling, Reaming, and Boring 

Drilling and reaming operations are performed 
in the horizontal boring mill as they are in a radial 



11-60 




Figure 11-89. Angular milling head. 



ui LJUC iiui izuiuai ooring iniii me 
is held in the horizontal position (fig. 1 1-90), while 
in the radial drill the tool is held in the vertical 
position. 



In Line Boring 

To set the horizontal boring machine for a line 
boring operation, insert a boring bar into the 
spindle and pass it through the work. The boring 
bar is supported on the foot end by the back rest 
assembly. Depending on the size of the bore 
required, you can use either standard or locally 
manufactured tooling. The head provides the 
rotary motion for the tools mounted in the boring 
bar. Align the work with the axis of the boring 
bar, and bolt and/or clamp it to the table. The 
cutting operation is usually performed by having 
the spindle move while the work is held stationary. 
However, you may, from time to time, find an 
operation in which you need to hold the bar in 




126.30 



Figure 11-90. Drilling in the horizontal boring mill. 



11-61 



a fixed position and move the table lengthwise to 
complete the operation. (See fig. 11-91.) 

The table can be power driven to provide 
travel perpendicular to the spindle, making it 
possible to bore, elongated and slotted when used 
in conjunction with vertical movement of the 
head. 

Some boring mills have a single spindle in the 
head while others have a secondary or auxiliary 
spindle that can be fitted with a precision 
head and used in some boring operations. This 
secondary spindle may also be used on light work 
such as drilling accurately spaced small holes. 

Reconditioning Split-Sleeve Bearings 

Practically all of the high-speed bearings the 
Navy uses on turbines are the babbitt-lined split- 
sleeve type. Once a bearing of this type has wiped, 
it must be reconditioned at the first opportunity. 
Wiped means that the bearing has been damaged 
by being run under an abnormal condition, such 
as without sufficient lubrication. If it has wiped 
only slightly, it can probably be scraped to a good 



bearing surface and restored to service. If it is 
badly wiped, it will have to be rebabbitted and 
rebored, or possibly replaced. 

When you receive a wiped bearing for repair, 
follow the procedure listed below as closely as 
possible: 

1. Check the extent of damage and wear 
marks. 

2. Take photos of the bearing to indicate the 
actual condition of the bearing and for future 
reference in the machining steps and reassembly. 

3. Check the shell halves for markings. A 
letter or number should be on each half for proper 
identification and assembly. (If the shell halves 
are not marked, mark them before you dis- 
assemble the bearing.) 

4. Inspect the outer shell for burrs, worn ends 
and the condition of alignment pins and holes. 

5. Check the blueprint and job order to ensure 
that required information has been provided to 
you. 

6. Ensure that the actual shaft size has not 
been modified from the blueprint. 




28.280 



Figure 11-91. Boring bar driven by the spindle and supported in the backrest block. 



uuw.il IAJ unv* uciav^ 



nit ouvn. 



the bearing shell with special cleaning solutions 
and rebabbitt them after plugging all oil holes with 
suitable material. 

After relining the shell, remove the excess bab- 
bitt extending above the horizontal flanges by 
rough machining on a shaper. Take extreme care 
to see that the base metal of the horizontal flanges 
is not damaged during this machining operation. 
After rough machining, blue the remaining excess 
babbitt and scrape it until no more excess bab- 
bitt extends above the horizontal flanges. 

Next, assemble the two half-shells and set 
them up on the horizontal boring mill. Check the 
spherical diameter of the bearing to ensure that 
it is not distorted beyond blueprint specifications 
according to NAVSHIPS 9411.813.2. Generally, 
the words "BORE TRUE TO THIS SURFACE" 
are inscribed on the front face of the bearing shell. 
When dialing in the bearing, be sure to dial in on 
this surface. 

Once you have properly aligned the bearing 
in the boring mill, you can complete practically 
all the other operations without changing the 
setup. Bore the bearing to the finished diameter 
and machine the oil grooves as required by 
blueprint specifications. 

Oil is distributed through the bearing by oil 
grooves. These grooves may be of several forms; 
the two simplest are axial and circumferential. 
Sometimes circumferential grooves are placed at 
the ends of the bearings as a controlling device 
to prevent side leakage, but this type of grooving 
does not affect the distribution of lubricant. 

When you machine grooves into a bearing, 
you must be careful in beveling the groove out 
into the bearing leads to prevent excess babbitt 
from clogging the oil passage. The type of grooves 
used in a bearing should not be changed from the 
original design, unless the change is warranted 
by continuous trouble traceable to improper 
lubricant distribution within the bearing. 

On completion of all machining operations, 
it is the responsibility of both the repair activity 
and the ship's force to determine that the bearing 
meets blueprint specifications and that a good 
bond exists between the shell and the babbitt 
metal. 

Threading 

Threads may be cut using the horizontal 
boring mill on machines that are equipped with 



is available. 

To cut threads with these machines, use a 
system of change gear combinations to obtain the 
different leads. Secure a single point tool in a 
suitable toolholder and mount the toolholder in 
the spindle of the machine. While you cut threads, 
keep the spindle locked in place. The saddle, 
carrying the workpiece, advances at a rate 
determined by the change gear combination. 
Feeding, in conjunction with the spindle rotation 
in the low back gear range, produces the threads. 

Cut the thread a little at a time in successive 
passes. The thread profile depends on how the 
cutting tool is ground. When you have completed 
the first pass, back the cutting tool off a few 
thousandths of an inch to avoid touching the 
workpiece on the return movement. Then reverse 
the spindle driving motor. This causes the saddle 
direction to reverse while the direction selection 
lever position remains unchanged. Allow the 
machine to run in this direction until the cutting 
tool has returned to its starting point. Advance 
the cutter to take out a little more stock, and after 
setting the spindle motor to run in forward, make 
another cutting pass. Follow this procedure until 
the thread is completed. A boring bar with a 
micro-adjustable tool bit or a small precision head 
is ideal for this operation. It allows fast, easy 
adjustment of the tool depth, plus accuracy and 
control of the depth setting. 

To set up for cutting threads, remove the 
thread lead access covers and set up the correct 
gear train combination as prescribed by- the 
manufacturer's technical manual. After you have 
set up the gear train, lock the sliding arm by 
tightening the nuts on the arm clamp. Be sure to 
replace the retaining washers on all the studs and 
lock them with the screws provided with the 
machine. Refer to the manufacturer's technical 
manual for the machine you are using for the 
correct gear arrangement. 

Some of the gear combinations use only one 
gear on the B stud. When this occurs, take up the 
additional space on the stud by adding spacers to 
the stud. The following check-off list will be of 
assistance to you in threading in a horizontal 
boring mill: 

1 . Be sure the correct change gears are on the 
proper centers. 

2. Position the head back-gear in the low 
range. 



11-63 



3 . Place the feed change lever in the correct 
position to release the standard feed. 

4. Engage the thread lead engaging lever. 

5. Shift the driving gear lever to the thread 
lead position. 

6. Start the spindle rotation forward. 

7. Place the saddle directional lever in the left 
position. It will remain in this position until the 
thread is completed. 

8. Place the feed/rapid traverse selector lever 
in the feed position. This will lock in the feed 
clutch until the threading operation is completed. 

9. To disengage the feed, place the thread lead 
driving gear lever in the standard position. The 
feed clutch will disengage. Do NOT do this during 
the threading operation or the thread lead timing 
will be lost. 



MILLING MACHINE 
SAFETY PRECAUTIONS 

Your first consideration as a Machinery 
Repairman should be your own safety. 
CARELESSNESS and IGNORANCE are the two 
great menaces to personal safety. Milling 
machines are not playthings and must be given 
the full respect that is due any machine tool. 

ft NEVER attempt to operate a machine 
unless you are sure that you understand it 
thoroughly. 

ft Do NOT throw an operating lever without 
knowing in advance what is going to take 
place. 



Do NOT play with the control levers or 
idly turn the handles of a milling machine, 
even if it is stopped. 

ft NEVER lean against or rest your hands on 
a moving table. If it is necessary to touch 
a moving part, know in advance the 
direction in which it is moving. 

ft Do NOT take a cut without making sure 
that the work is held securely in the vise 
or fixture and that the holding member is 
rigidly fastened to the machine table. 

Always remove chips with a brush or other 
suitable tool; NEVER use fingers or hands. 

Before attempting to operate any milling 
machine, study it thoroughly. Then if an 
emergency arises, you can stop the 
machine immediately. Knowing how to 
stop a machine is just as important, if not 
more important, as knowing how to start 
it. 

ft You must above all KEEP CLEAR OF 
THE CUTTERS. Do NOT touch a cutter, 
even when it is stationary, unless there is 
good reason to do so, and then be very 
careful. 

The milling machine is not dangerous to 
operate, but if you do not follow certain safety 
practices you are likely to find it dangerous. There 
is always the danger of getting caught in the 
cutter. Never attempt to remove chips with your 
fingers at the point of contact of the cutter and 
the work. There is danger to your eyes from flying 
chips, so always protect your eyes with goggles 
and keep your eyes out of the line of cutting 
action. 



SHAPERS, PLANERS, AND ENGRAVERS 



In this chapter we will discuss the major types 
of shapers, planers, and pantographs (engravers), 
and their individual components, cutters, and 
operating principles and procedures. A shaper has 
a reciprocating single-edged cutting tool that 
removes metal from the work as the work is fed 
into the tool. A planer operates on a similar 
principle except that the work reciprocates, and 
the tool is fed into the work. A pantograph is used 
primarily for engraving letters and designs on any 
type of material. A pantograph can be used to 
engrave concave, convex, and spherical surfaces 
as well as flat surfaces. 



SHAPERS 

A shaper has a reciprocating ram that carries 
a cutting tool. The tool cuts only on the 
forward stroke of the ram. The work is held in 
a vise or on the worktable, which moves at 
a right angle to the line of motion of the 
ram, permitting the cuts to progress across 
the surface being machined. A shaper is 
identified by the maximum size of a cube it can 
machine; thus, a 24-inch shaper will machine a 
24-inch cube. 



TYPES OF SHAPERS 

There are three distinct types of shapers 
crank, geared, and hydraulic. The type depends 
on how the ram receives motion to produce its 
own reciprocating motion. In a crank shaper the 
ram is moved by a rocker arm, which is driven 
by an adjustable crankpin secured to the main 
driving gear. Quick return of the ram is a feature 
of a crank shaper. In a geared shaper, the ram 
is moved by a spur gear, which meshes with a rack 
secured to the bottom of the ram. In a hydraulic 
shaper, the ram is moved by a hydraulic cylinder 



whose piston rod is attached to the bottom of the 
ram. Uniform tool pressure, smooth drive, and 
smooth work are features of the hydraulic-type 
shaper. 

There are many different makes of shapers, 
but the essential parts and controls are the same 
on all. When you learn how to operate one make 
of shaper, you should not have too much trouble 
in learning to operate another make. Figure 12-1 
is an illustration of a crank shaper found in shops 
in some Navy ships. 



SHAPER ASSEMBLIES 

To perform the variety of jobs you will be 
required to do using the shaper, you must know 
the construction and operation of the main 
components. Those components are the main 
frame assembly, drive assembly, crossrail 
assembly, toolhead assembly, and table feed 
mechanism. (See fig. 12-2.) 



Main Frame Assembly 

The main frame assembly consists of the base 
and the column. The base houses the lubricating 
pump and sump, which provide forced lubrica- 
tion to the machine. The column contains 
the drive and feed actuating mechanisms. A 
dovetail slide is machined on top of the column 
to receive the ram. Vertical flat ways are machined 
on the front of the column to receive the cross- 
rail. 



Drive Assembly 

The drive assembly consists of the ram and 
the crank assembly. These parts convert the rotary 
motion of the drive pinion to the reciprocating 



12-1 




BASE 



28.219X 



Figure 12-1. Standard shaper. 



motion of the ram. By using the adjustments 
provided, you can increase or decrease the length 
of stroke of the ram, and can also position the 
ram so that the stroke is in the proper area in 
relation to the work. 

You can adjust the CRANKPIN, which is 
mounted on the crank gear, from the center of 
the crank gear outward. The sliding block fits over 
the crankpin and has a freesliding fit in the rocker 
arm. If you center the crankpin (and therefore the 
sliding block) on the axis of the crank gear, the 
rocker arm will not move when the crank gear 
turns. But if you set the crankpin off center (by 



turning the stroke adjusting screw), any motion 
of the crank gear will cause the rocker arm 
to move. This motion is transferred to the 
ram through the ram linkage and starts the 
reciprocating motion of the ram. The distance the 
crankpin is set off center determines the length 
of stroke of the tool. 

To position the ram, turn the ram position- 
ing screw until the ram is placed properly with 
respect to the work. Specific procedures for 
positioning the ram and setting the stroke are in 
the manufacturer's technical manual for the 
specific machines you are using. 



12-2 



TOOLHEAD 
CLAPPER BOX 



TOOLPOST 



WORKTABLE 




RAM LINKAGE 



UPPER ROCKER 
PIVOT 



CRANK GEAR 
DRIVING PINION 



ROCKER ARM 



LOWER ROCKER 
PIVOT 



Figure 12-2. Cross-sectional view of a crank type shaper. 



Crossrail Assembly 

The crossrail assembly includes the crossrail, 
the crossfeed screw, the table, and the table 
support bracket (foot). (See fig. 12-1.) The 
crossrail slides on the vertical ways on the front 
of the shaper column. The crossrail apron 
(to which the worktable is secured) slides on 
horizontal ways on the crossrail. The crossfeed 
screw engages in a mating nut, which is secured 
to the back of the apron. The screw can be turned 
either manually or by power to move the table 
horizontally. 

The worktable may be plain or universal as 
shown in figure 12-3. Some universal tables can 
be swiveled only right or left, away from the 
perpendicular; others may be tilted fore or aft at 
small angles to the ram. T-slots on the worktables 
are for mounting the work or work-holding 
devices. A table support bracket (foot) holds the 
worktable and can be adjusted to the height 
required. The bracket slides along a flat surface on 
the base as the table moves horizontally. The table 
can be adjusted vertically by the table elevating 
screw (fig. 12-2). 




28.221X 



Figure 12-3. Swiveled and tilted table. 



12-3 



Table Feed Mechanism 

The table feed mechanism (fig. 12-4) consists 
of a ratchet wheel and pawl, a rocker, and a feed 
drive wheel. The feed drive wheel (driven by the 
main crank), which operates similarly to the ram 
drive mechanism, converts rotary motion to 
reciprocating motion. As the feed drive wheel 
rotates, the crankpin (which can be adjusted off 
center) causes the rocker to oscillate. The straight 
face of the pawl pushes on the back side of a tooth 
on the ratchet wheel, turning the ratchet wheel 
and the feed screw. The back face of the pawl is 
cut at an angle to ride over one or more teeth as 
it is rocked in the opposite direction. To change 
the direction of feed, lift the pawl and rotate it 
one-half turn. To increase the rate of feed, 
increase the distance between the feed drive wheel 
crankpin and the center of the feed drive wheel. 

The ratchet wheel and pawl method of feeding 
crank-type shapers has been used for many years. 
Relatively late model machines still use similar 
principles. As specific procedures for operating 
feed mechanisms may vary, you should consult 
manufacturers' technical manuals for explicit 
instructions. 

Toolhead Assembly 

The toolhead assembly consists of the 
toolslide, the downfeed mechanism, the clapper 
box, the clapper head, and the toolpost at the 
forward end of the ram. The entire assembly can 
be swiveled and set at any angle not exceeding 50 
on either side of the vertical. The toolhead is 
raised or lowered by hand feed to make vertical 
cuts on the work. In making vertical or angular 
cuts, the clapper box must be swiveled away from 



the surface to be machined (fig. 12-5); otherwise, 
the tool will dig into the work on the return stroke. 

SHAPER VISE 

The shaper vise is a sturdy mechanism secured 
to the table by T-bolts. The vise has two jaws, 
one stationary, the other movable, that can be 



DOWNFEED MECHANISM 



TOOLPOST 




CLAPPER HEAD 
CLAPPER BOX 



TOOLSLIDE 
POSITION FOR HORIZONTAL CUTTING 




POSITIONS FOR DOWN CUTTING 



Figure 12-5. Toolhead assembly in various positions. 



WORK 



PAWL, 



RATCHET, 
WHEEL 



FEED- 
SCREW 



-CONTROL KNOB 

ROCKER (OSCILLATES 
ON FEED SCREW) 

FEED DRIVE WHEEL 

CONNECTING CRANKPIN (ADJUSTABLE 

LINKAGE TOWARD OR AWAY FROM 

CENTER OF WHEEL) 

FEED DRIVE 
WHEEL 



C-CLAMPS 



PARALLEL 




ANGLE PLATE 



TABLE 



deeper and will open to accommodate large work. 
Most such vises have hardened steel jaws ground 
in place. The universal vise may be swiveled in 
a horizontal plane from to 180. The usual 
positions have the jaws set either parallel with the 
stroke of the ram or at a right angle to the stroke. 
See that the vise is free from any obstruction that 
might keep the work from seating properly. 
Remove burrs and rough edges on the vise and 
chips left from previous machining before 
starting to work. 

Work can be set on parallels so the surface 
to be cut is above the top of the vise. Shaper hold- 
downs can be used in holding the work between 
the jaws of the vise (fig. 12-6). Work larger than 
the vise will hold can be clamped directly to the 
top or side of the machine table. When work too 
large or awkward for a swivel vise must be 



also used in mounting work on shaper tables. 
TOOLHOLDERS 

Various types of toolholders, made to hold 
interchangeable tool bits, are used to a great 
extent in planer and shaper work. Tool bits are 
available in different sizes and are hardened and 
cut to standard lengths to fit the toolholders. The 
toolholders that you will most commonly use are 
(fig. 12-7): 

1. Right-hand, straight, and left-hand 
toolholders, which may be used for the majority 
of common shaper and planer operations. 

2. Gang toolholders, which are especially 
adapted for surfacing large castings. With a gang 
toolholder you make multiple cuts with each 





LEFT-HAND, STRAIGHT, AND RIGHT-HAND TOOLHOLDERS GANG TOOLHOLDER AND MULTIPLE CHIP PRODUCED 







SWIVEL HEAD TOOLHOLDER 



SPRING TOOLHOLDER 





EXTENSION TOOLHOLDER 



Figure 12-7. Toolholders. 



12-5 



forward stroke of the shaper. Each tool takes a 
light cut and there is less tendency to ' 'break out' ' 
at the end of a cut. 

3. Swivel head toolholders, which are univer- 
sal, patented holders that may be adjusted to place 
the tool in various radial positions. This feature 
allows the swivel head toolholder to be converted 
into a straight, right-hand, or left-hand holder at 
will. 

4. Spring toolholders, which have a rigid 
U-shaped spring that lets the holder cap absorb 
a considerable amount of vibration. A spring 
toolholder is particularly good for use with 
formed cutters, which have a tendency to chatter 
and dig into the work. 

5. Extension toolholders, which are adapted 
for cutting internal keyways, splines, and grooves 
on the shaper. The extension arm of the holder 
can be adjusted to change the exposed length and 
the radial position of the tool. 

Procedures for grinding shaper and planer tool 
bits for various operations are discussed in 
Chapter 6 of this training manual. 



SHAPER SAFETY PRECAUTIONS 

The shaper, like all machines in the machine 
shop, is not a dangerous piece of equipment if 
you observe good safety practices. You should 
read and understand the safety precautions and 
operating instructions posted on or near a shaper 
prior to operating it. Some good safety practices 
are listed here but are intended only to supple- 
ment those posted on the machine. 

9 Always wear goggles or a face shield. 

9 Ensure that the workpiece, vise, and setup 
fixture are properly secured. 

Ensure that the work area is clear of tools. 

Inform other personnel in the area to 
prevent possible injury to them from flying 
chips. 

9 Ensure that the travel of the ram is clear 
to both the front and the rear of the 
machine. 

Never stand in front of the shaper while 
it is in operation. 



Avoid touching the tool, the clapper box, 
or the workpiece while the machine is in 
operation. 

Never remove chips with your bare hand; 
always use a brush or a piece of wood. 

Keep the area around the machine clear of 
chips to help prevent anyone from slipping 
and falling into the machine. 

9 Remember: SAFETY FIRST, ACCU- 
RACY SECOND, SPEED LAST. 



SHAPER OPERATIONS 

Before beginning any job on the shaper, you 
should thoroughly study and understand the 
blueprint or drawing from which you are to work. 
In addition, you should take the following 
precautions: 

Make certain that the shaper is well oiled. 

Clean away ALL chips from previous 
work. 

9 Be sure that the cutting tool is set 
properly; otherwise the tool bit will 
chatter. Set the toolholder so the tool bit 
does not extend more than about 2 inches 
below the clapper box. 

Be sure the piece of work is held rigidly 
in the vise to prevent chatter. You can seat 
the work by tapping it with a babbitt 
hammer. 

9 Test the table to see if it is level and square. 
Make these tests with a dial indicator and 
a machinist's square as shown in figure 
12-8. If either the table or the vise is off 
parallel, check for dirt under the vise or 
improper adjustment of the table support 
bracket. 

Adjust the ram for length of stroke and 
position. The cutting tool should travel 1/8 
to 1/4 inch past the edge of the work on 
the forward stroke and 3/4 to 7/8 inch 
behind the rear edge of the work on the 
return stroke. 



12-6 




JOINT 

Figure 12-8. Squaring the table and the vise. 



28.226 



Speeds and Feeds 

Setting up the shaper to cut a certain material 
is similar to setting up other machine tools, such 
as drill presses and lathes. First, you have to 
determine the approximate required cutting speed 
and then you have to determine and set the 
necessary machine speed to produce your desired 
cutting speed. On all of the machine tools we 
discussed in the previous chapters, cutting speed 
was directly related to the speed (rpm) of the 
machine's spindle. You could determine what 
spindle rpm to set by using one formula for all 
brands of a particular type of machine. Setting 
up a shaper is slightly different. You still relate 
cutting speed to machine speed through a 
formula, but the formula that you use depends 
on the brand of machine that you operate. This 
is because some manufacturers use a slightly 
different formula for computing cutting speed 



than others. To determine what specific formula 
to use for your machine, consult the operator's 
manual provided by the manufacturer. 

The following discussion explains basically 
how the operation of a shaper differs from the 
operations of other machine tools. It also explains 
how to determine the cutting speeds and related 
machine speeds for a Cincinnati shaper. 

Whenever you determine the speed of the 
shaper required to produce a particular cutting 
speed, you must account for the shaper's 
reciprocating action. This is because the tool only 
cuts on the forward stroke of the ram. In most 
shapers the time required for the cutting stroke 
is 1 1/2 times that required for the return stroke. 
This means that in any one cycle of ram action 
the cutting stroke consumes 3/5 of the time and 
the return stroke consumes 2/5 of the time. The 
formula for determining required machine strokes 



12-7 



contains a constant that accounts for this partial 
time consumption by the cutting stroke. 

To determine a cutting stroke value to set 
on the shaper speed indicator, first select a 
recommended cutting speed for the material you 
plan to shape from a chart such as the one shown 
in table 12-1. 

After you have selected the recommended 
cutting speed, determine the ram stroke speed by 
using the formula shown below (remember, your 
machine may require a slightly different formula): 



SPM = 



CS 



0.14 x LOS 



Where: SPM = strokes of the ram per minute 

CS = cutting speed in feet per 
minute 

LOS = length of stroke in inches 

0.14 = constant that accounts for 
partial ram cycle time and that 
converts inches to feet 

When you have determined the number of 
strokes per minute, set it on the shaper by using 
the gear shift lever. A speed (strokes) indicator 
plate shows the positions of the lever for a variety 
of speeds. Take a few trial cuts and adjust the ram 
speed slightly, as necessary, until you obtain the 
desired cut on the work. 

If after you have adjusted the ram speed, you 
want to know the exact cutting speed of the tool, 
use the formula: 

CS = SPM x LOS x 0.14 

The speed of the shaper is regulated by the 
gear shift lever. The change gear box, located on 
the operator's side of the shaper, lets you change 
the speed of the ram and cutting tool according 
to the length of the work and the hardness of the 
metal. When the driving gear is at a constant 
speed, the ram will make the same number of 
strokes per minute regardless of whether the 
stroke is 4 inches or 12 inches. Therefore, to main- 
tain the same cutting speed, the cutting tool must 
make three times as many strokes for the 4-inch 
cut as it does for the 12-inch cut. 

Horizontal feed rates of up to approximately 
0.170 inch per stroke are available on most 
shapers. There are no hard and fast rules for 
selecting a specific feed rate in shaping. Therefore, 



when you select feeds, you must rely on past 
experience and common sense. Generally, for 
making roughing cuts on rigidly held work, set 
the feed as heavy as the machine will allow. For 
less rigid setups and for finishing, use light feeds 
and small depths of cut. The best procedure is to 
start with a relatively light feed and increase the 
feed until you reach a desirable feed rate. 

Shaping a Rectangular Block 

An accurately machined rectangular block has 
square corners and opposite surfaces that are 
parallel to each other. In this discussion, faces are 
the surfaces of the block that have the largest 
surface area; the ends are the surfaces that limit 
the length of the block; and the sides are the 
surfaces that limit the width of the block. 

The rectangular block can be machined in four 
setups when a shaper vise is used. One face and 
an end are machined in the first setup. The 
opposite face and end are machined in the second 
setup. The sides are machined in two similar but 
separate setups. For both setups, the vise jaws are 
aligned at a right angle to the ram. 

To machine a rectangular block from a rough 
casting, proceed as follows: 

1 . Clamp the casting in the vise so a face is 
horizontally level and slightly above the top of 
the vise jaws. Allow one end to extend out of the 
side of the vise jaws enough so you can take a 
cut on the end without unclamping the casting. 
Now feed the cutting tool down to the required 
depth and take a horizontal cut across the face. 
After you have machined the face, readjust the 
cutting tool so it will cut across the surface of the 
end that extends from the vise. Use the horizontal 
motion of the ram and the vertical adjustment of 
the toolhead to move the tool across and down 
the surface of the end. When you have machined 
the end, check to be sure that it is square with 
the machined face. If it is not square, adjust the 
toolhead swivel to correct the inaccuracy and take 
another light finishing cut down the end. 

2. To machine the second face and end, turn 
the block over and set the previously machined 
face on parallels (similar to the method used in 
step 1). Insert small strips of paper between each 
corner of the block and the parallels. Clamp the 
block in the vise and use a soft-face mallet to tap 
the block down solidly on the parallels. When the 
block is held securely in the vise, machine the 
second face and end to the correct thickness and 
length dimensions of the block. 



12-8 



ijrpc u* uictcxi. 


\stni uuu sicei LUUI& 


niga- speeu sieei LOUIS 


Roughing 


Finishing 


Roughing 


Finishing 




30 
25 
20 

} 

75 


20 
40 
30 

100 
100 


60 
50 
40 

150 
150 


40 
80 
60 

200 
200 


Milri cstpipl -- 


Tnrvl cfAol _____..__..___ 











3. To machine a side, open the vise jaws so 
the jaws can be clamped on the ends of the block. 
Now set the block on parallels in the vise with the 
side extending out of the jaws enough to permit 
a cut using the downfeed mechanism. Adjust the 
ram for length of stroke and for position to 
machine the side and make the cut. 

4. Set up and machine the other side as 
described in step 3. 

Shaping Angular Surfaces 

Two methods are used for machining angular 
surfaces. For steep angles, such as on V-blocks, 
the work is mounted horizontally level and the 
toolhead is swiveled to the desired angle. For small 
angles of taper, such as on wedges, the work is 
mounted on the table at the desired angle from 
the horizontal, or the table may be tilted if the 
shaper is equipped with a universal table. 

To machine a steep angle using the toolhead 
swiveled to the proper angle: 

1 . Set up the work as you would to machine 
a flat surface parallel with the table. 

2. Swivel the toolhead (fig. 12-5) to the 
required angle. (Swivel the clapper box in the 
opposite direction.) 

3. Start the machine and, using the manual 
feed wheel on the toolhead, feed the tool down 
across the workpiece. Use the horizontal feed 
control to feed the work into the tool and to 
control the depth of cut (thickness of the chip). 
(Because the tool is fed manually, be careful to 
feed the tool toward the work only during the 
return stroke.) 



4. Set up and machine the other side as 
described in step 3. 

Shaping Key ways in Shafts 

Occasionally, you may have to cut a key way 
in a shaft by using the shaper. Normally, you will 
lay out the length and width of the keyway on the 
circumference of the shaft. A center line laid out 
along the length of the shaft and across the end 
of the shaft will make the setup easier (fig. 12-9, 
view A). Figure 12-9 also shows holes of the same 
diameter as the keyway width and slightly deeper 
than the key drilled into the shaft. These holes 
are required to provide tool clearance at the 




/""""""' 1 "-""> m """l' ""Y""""' 
j J^ j 


I'")"" 







Figure 12-9. Cutting a keyway in the middle of a shaft. 



12-9 



beginning and end of the cutting stroke. The holes 
shown in figure 12-9 are located for cutting a blind 
key way (not ending at the end of a shaft). If the 
key way extends to the end of the shaft, only one 
hole is necessary. 

To cut a keyway in a shaft, proceed as follows: 

1 . Lay out the centerline, the keyway width, 
and the clearance hole centers as illustrated in part 
A of figure 12-9. Drill the clearance holes. 

2. Position the shaft in the shaper vise or on 
the worktable so that it is parallel to the ram. 
Use a machinist's square to check the centerline 
on the end of the shaft to ensure that it is 
perpendicular to the surface of the worktable. 
This ensures that the keyway layout is exactly 
centered at the uppermost height of the shaft, to 
provide a keyway that is centered on the 
centerlines of the shaft. 

3. Adjust the stroke and the position of the 
ram, so the forward stroke of the cutting tool ends 
at the center of the clearance hole. (If a blind 
keyway is being cut, ensure that the cutting tool 
has enough clearance at the end of the return 
stroke so the tool will remain in the keyway slot.) 
(See view B of fig. 12-9.) 

4. Position the work under the cutting tool 
so that the tool's center is aligned with the 
centerline of the keyway. (If the keyway is 



over 1/2 inch wide, cut a slot down the center and 
shave each side of the slot until you obtain the 
proper width. 

5. Start the shaper and, using the toolhead 
slide, feed the tool down to the depth required, 
as indicated by the graduated collar. 

Shaping an Internal Keyway 

To cut an internal keyway in a gear, you will 
have to use extension tools. These tools lack the 
rigidity of external tools, and the cutting point 
will tend to spring away from the work unless you 
take steps to compensate for this condition. The 
keyway MUST be in line with the axis of the gear. 
Test the alignment with a dial indicator by taking 
a reading across the face of the gear; swivel the 
vise slightly, if necessary, to correct the alignment. 

The bar of the square-nose toolholder should 
not extend any farther than necessary from the 
shank; otherwise the bar will have too much 
"spring" and will allow the tool to be forced out 
of the cut. 

The extension toolholder should extend as far 
as practical below the clapper block, rather than 
in the position shown by the dotted lines in view 
A of figure 12-10. The pressure angle associated 
with the toolholder in the upper position may 
cause the pressure of the cut to open the clapper 
block slightly and allow the tool to leave the cut. 



PRESSURE ANGLE OF 
TOOL IN UPPER AND 
LOWER POSITIONS 




SQUARE NOSE TOOL 




X (CROWN) 



B 



opening. Another method for preventing the 
clapper block from opening is to mount the tool 
in an inverted position. 

With the cutting tool set up as in view A of 
figure 12-10, center the tool within the layout lines 
in the usual manner, and make the cut to the 
proper depth while feeding the toolhead down by 
hand. Within the setup in an inverted position, 
center the tool within the layout lines at the top 
of the hole, and make the cut by feeding the 
toolhead upward. 

The relative depths to which external and 
internal keyways are cut to produce the greatest 
strength are illustrated by view B of figure 12-10. 
In cutting a key way in the gear, the downfeed 
micrometer collar is set to zero at the point where 
the cutting tool first touches the edge of the hole. 
The crown, X, is first removed from the shaft to 
produce a flat whose width is equal to the width 
of the key. Then the cut is made in the shaft to 
depth Z. The distance of "Y" plus "Z" is equal 
to the height of the key that is to lock the two 
parts together. (See fig. 12-10.). 



Shaping Irregular Surfaces 

You can machine irregular surfaces by using 
form ground tools and by hand feeding the 
cutting tool vertically while using power feed to 
move the work horizontally. An example of work 
that you might shape by using form tools is a gear 
rack. You can shape work such as concave and 
convex surfaces by using the toolhead feed. When 
you machine irregular surfaces, you have to pay 
close close attention because you control the 
cutting tool manually. Also in this work you 
should lay out the job before you machine it to 
provide reference lines. You should also take 
roughing cuts to remove excess material to within 
1/16 inch of the layout lines. 

You can cut RACK TEETH on a shaper as 
well as on a planer or a milling machine. During 
the machining operation, you may either hold 
the work in the vise or clamp it directly to 
the worktable. After you have mounted and 
positioned the work, rough out the tooth space 
in the form of a plain rectangular groove with a 
roughing tool, then finish it with a tool ground 
to the tooth's finished contour and size. 



1 . Clamp the work in the vise or to the table. 

2. Position a squaring tool, which is 
narrower than the required tooth space, so the 
tool is centered on the first tooth space to be cut. 

3. Set the graduated dial on the crossfeed 
screw to zero, and use it as a guide for spacing 
the teeth. 

4. Move the toolslide down until the tool just 
touches the work and lock the graduated collar 
on the toolslide feed screw. 

5. Start the machine and feed the toolslide 
down slightly less than the whole depth of the 
tooth, using the graduated collar as a guide, and 
rough out the first tooth space. 

6. Raise the tool to clear the work and move 
the crossfeed a distance equal to the linear pitch 
of the rack tooth by turning the crossfeed lever. 
Rough out the second tooth space and repeat this 
operation until all spaces are roughed out. 

7. Replace the roughing tool with a tool 
ground to size for the tooth form desired, and 
align the tool. 

8. Adjust the work so the tool is properly 
aligned with the first tooth space that you rough 
cut. 

9. Set the graduated dial on the crossfeed 
screw at zero and use it as a guide for spacing the 
teeth. 

10. Move the toolslide down until the tool just 
touches the work and lock the graduated collar 
on the toolslide feed screw. 

1 1 . Feed the toolslide down the whole depth 
of the tooth, using the graduated collar as a guide, 
and finish the first tooth space. 

12. Raise the tool to clear the work and move 
the crossfeed a distance equal to the linear pitch 
of the rack tooth by turning the crossfeed lever. 

13. Finish the second tooth space, then 
measure the thickness of the tooth with the gear 
tooth vernier caliper. Adjust the toolslide to 
compensate for any variation indicated by this 
measurement. 

14. Repeat the process of indexing and cutting 
until you have finished all of the teeth. 

Irregular surfaces commonly machined on 
the shaper have both CONVEX and CON- 
CAVE radii. On one end of the work, lay 
out the contour of the finished job. When you 
shape to a scribed line, as illustrated in 



12-11 



figure 12-11, it is good practice to rough cut to 
within 1/16 inch of the line. You can do this by 
making a series of horizontal cuts using automatic 
feed and removing excess stock. Use a left-hand 
cutting tool to remove stock on the right side of 
the work and a right-hand cutting tool to remove 
stock on the left side of the work. When 1/16 inch 
of metal remains above the scribed line, take a 
file and bevel the edge to the line. This will 
eliminate tearing of the line by the breaking of 
the chip. Starting at the right-hand side of the 
work, set the automatic feed so the horizontal 
travel is rather slow and, feeding the tool vertically 
by hand, take the finishing cuts to produce a 
smooth contoured surface. 

VERTICAL SHAPERS 

The vertical shaper (slotter) shown in figure 
12-12 is especially adapted for slotting internal 
holes or key ways with angles up to 10. Angular 
slotting is done by tilting the vertical ram 
(fig. 12-12), which reciprocates up and down, to 
the required angle. Although different models of 
machines will have their control levers in different 
locations, all of them will have the same basic 
functions and capabilities. The speed of the ram 
is adjustable to allow for the various materials and 
machining requirements and is expressed in either 



strokes per minute or feet per minute, depending 
on the particular model. The length and the 
position of the ram stroke may also be adjusted. 
Automatic feed for the cross and longitudinal 
movements, and on some models the rotary move- 
ment, is provided by a ratchet mechanism, gear 
box, or variable speed hydraulic system, again, 
depending on the model. Work may be held in 
a vise mounted on the rotary table, clamped 
directly to the rotary table, or held by special 
fixtures. The square hole in the center of a valve 
handwheel is an example of work that can be done 
on a machine of this type. The sides of the hole 
are cut on a slight angle to match the angled sides 
of the square on the valve stem. If this hole were 
cut by using a broach or an angular (square) hole 
drill, the square would wear prematurely due to 
the reduced area of contact between the straight 
and angular surfaces. 

PLANERS 

Planers are rigidly constructed machines, 
particularly suitable for machining large and 
heavy work where long cuts are required. In 
general, planers and shapers can be used for 
similar operations. However, the reciprocating 
motion of planers is provided by the worktable 
(platen), while the cutting tool is fed at a right 




Figure 12-ll.~Shaping irregular surfaces. 



28.227 




VERTICAL 
RAM 



TOOLHEAD 



CUTTING TOOL 

ROTARY 
TABLE 



TRANSVERSE 

FEED 

HANDWHEEL 



LEVER 

FEEDING 
MECHANISM 

COLUMN 



BASE 



LONGITUDINAL FEED 
HANDWHEEL 



Figure 12-12. Vertical shaper. 



table makes a quick return to bring the work 
into position for the next cut. The size of a planer 
is determined by the size of the largest work that 
can be clamped and machined on its table; thus 
a 30 inch by 30 inch by 6 foot planer is one that 
can accommodate work up to these dimensions. 

TYPES OF PLANERS 

Planers are divided into two general classes, 
the OPEN side type and the DOUBLE HOUS- 
ING type. 

Planers of the open side type (fig. 12-13) 
have a single vertical housing to which the 
crossrail is attached. The advantage of this 
design is that work that is too wide to pass 



0W CONTROL IE.VW 
CSPESD COHTROO 




28.230X 



Figure 12-13. Open side planer. 



12-13 



between the uprights of a double housing machine 
may be planed. 

In the double housing planer, the worktable 
moves between two vertical housings to which a 
crossrail and toolhead are attached. The larger ma- 
chines are usually equipped with the cutting heads 
mounted to the crossrail as well as a side head 
mounted on each housing. With this setup, it is 
possible to simultaneously machine both the side 
and the top surfaces of work mounted on the table. 

CONSTRUCTION AND 

MAINTENANCE 

All planers consist of five principal parts: the 
bed, table, columns, crossrail, and the toolhead. 

The bed is a heavy, rigid casting that supports 
the entire piece of machinery. On the upper 
surface of the bed are the ways on which the 
planer table rides. 

The table is a cast iron flat surface to which 
the work is mounted. The planer table has T-slots 
and reamed holes for fastening work to the table. 
On the underside of the table there is usually a 
gear train or a hydraulic mechanism, which gives 
the table its reciprocating motion. 

The columns of a double housing planer are 
attached to either side of the bed and at one end 
of the planer. On the open side planer there is only 
one column or housing attached on one side of 
the bed. The columns support and carry the 
crossrail. 

The crossrail serves as the rigid support for 
the toolheads. The vertical and horizontal feed 
screws on the crossrail enable you to adjust the 
machine for various size pieces of work. 

The toolhead is similar to that of the shaper 
in construction and operation. 

All sliding surfaces subject to wear are 
provided with adjustments. Keep the gibes 
adjusted to take up any looseness due to wear. 

OPERATING THE PLANER 

Before you operate a planer, be sure you know 
where the various controls are and what function 
each controls. Once you have mastered the opera- 
tion of one model or type of planer you will have 
little difficulty in operating others. You should, 
however, refer to the manufacturer's technical 
manual for the machine you are using for specific 
operating instructions. The following sections 
contain general information on planer operation. 

Table Speeds 

The table speeds are controlled by the start- 
stop lever and the flow control lever (fig. 12-13). 



Two ranges of speeds and a variation of speeds 
within each range are available. The speed range 
(LOW-MAXIMUM CUT or HIGH-MINIMUM 
CUT) is selected by using the start-stop lever, and 
the speeds within each range are varied by using 
the flow control lever. As the flow control lever 
is moved toward the right, the table speed will 
gradually increase until it reaches the highest 
possible speed. 

The LOW speed range is for shaping hard 
materials, which require high cutting force at low 
speeds. The HIGH range is for softer materials, 
which require less cutting force but higher cut- 
ting speeds. 

The RETURN speed control provides two 
return speed ranges (NORMAL and FAST). 
When NORMAL is selected, the return speed 
varies in ratio with the cutting speed selected. In 
FAST, the return speed remains constant (full 
speed), independent of the cutting speed setting. 



Feeds 

Feed adjustment is made by turning the hand- 
wheel, which controls the amount of toolhead 
feed. Turning the handwheel counterclockwise 
increases the feed. The amount of feed can be read 
on the graduated dials at the operator's end of 
the crossrail feed box. Each graduation indicates 
a movement of 0.001 inch. 

The direction of feed (right or left, up or 
down) of the toolhead is controlled by the lever 
on the rear of the feed box. The vertical feed is 
engaged or disengaged by the upper of the two 
levers on the front of the feed box. Shifting the 
rear, or directional, lever to the down position and 
engaging the clutch lever by pressing it downward 
gives a downward feed to the toolhead. Shifting 
the directional lever to the up position gives an 
upward feed. 

The lower clutch lever on the front of the feed 
box engages the horizontal feed of the toolhead. 
When the directional lever on the rear of the box 
is in the down position, the head is fed toward 
the left. When the directional lever is in the up 
position, the head is fed toward the right. Shifting 
the directional lever to the up position gives an 
upward feed. 

The ball crank on top of the vertical slide 
(toolhead feed) is used to hand feed the toolslide 
up or down. A graduated dial directly below the 
crank indicates the amount of travel. 

The two square-ended shafts at the end of the 
crossrail are used to move the toolhead by hand. 



03 ill Lilt 



neutral, position, and then turn the shaft. The 
upper shaft controls vertical movement. The lower 
shaft controls horizontal movement. 

Lock screws on both the cross-slide saddle and 
the vertical slide enable these slides to be locked 
in position after the desired tool setting is made. 

The planer side head has power vertical feed 
and hand horizontal feed. The vertical feed, both 
engagement and direction, is controlled by a lever 
on the rear of the side head feed box. Vertical 
traverse is done by turning the square shaft that 
projects from the end of the feed box. Horizontal 
movement, both feed and traverse, is done by 
using the bellcrank on the end of the toolhead 
slide. 

Rail Elevation 

The crossrail is raised or lowered by a hand- 
crank on the squared shaft projecting form the 
rear of the rail brace. To move the rail, first loosen 
the two clamp nuts at the rear of the column and 
the two clamp nuts at the front; then with the 
handcrank move the rail to the desired height. Be 
sure to tighten the clamp nuts before you do any 
machining. 

On machines that have power rail elevation, 
a motor is mounted within the rail brace and 
connected to the elevating mechanism. Operation 
of the motor, forward or reverse, is controlled by 
pushbuttons. The clamp nuts have the same use 
on all machines whether manual or power eleva- 
tion is used. 

Holding the Work 

The various accessories used in planer or 
shaper work may make the difference between a 
superior job and a poor job. There are no set rules 
on the use of planer accessories for clamping 
down a piece of work results will depend on 
your ingenuity and experience. 

One way to hold down work on the worktable 
is by using clamps. The clamps are attached to 
the worktable by bolts inserted in the T-slots. 
Figure 12-14 illustrates a step block used with the 
clamps shown in figure 5-30. At some time you 
may have to clamp an irregularly shaped piece of 
work to the planer table. One way to do this is 
illustrated in figure 12-15; here an accurately 
machined step block is used with a gooseneck 
clamp. Figure 12-16 illustrates correct and 
incorrect ways to apply clamps. 




Figure 12-14. Step block. 



-STEP BLOCK GOOSENECK WORK 

CLAMP 



I 




MACHINE TABLE 



Figure 12-15. Application of step block and clamp. 



^ 


.OCK ^ ^BLOCK ^ 






SS 




WORK ^ > 






| 




WORK / 



CORRECT 



INCORRECT 




CORRECT 



INCORRECT 



BLOCK 



STRIP 



BLOCK 




WORK 



IWORK! 



CORRECT 



INCORRECT 



^ 


,OCK inl ^-BLOCK iTTl 


1 ' ' " . i x r ' ^i 






i 


r~ui 






i 


\ ^ 


CORRECT INCORRECT 




CORRECT 



INCORRECT 



Figure 12-16. Correct and incorrect clamp applications. 



12-15 



For leveling and supporting work on the 
planer table, jacks of different sizes are used. The 
conical point screw (fig. 12-17) replaces the swivel 
pad type screw for use in a corner. Extension bases 
(fig. 12-17, C, D, E, and F) are used for increasing 
the effective height of the jack. 



planer, unlike the surface grinder, has no built-in 
protection against the grinding particles left by 
the grinding operation. 

Observe the same safety precautions for the 
shaper as you do for the planer. Always observe 
standard machine shop practices. 



SURFACE GRINDING 
ON THE PLANER 

While it is not a recommended practice, it is 
possible, with the use of a toolpost grinder, to use 
the planer as a surface grinder. Most of the large 
tender and repair type ships of the Navy have 
surface grinders on board, but due to space 
limitations this machine may not always have a 
large enough capacity to accommodate large work 
pieces. It sometimes may become necessary to use 
the planer as a surface grinder. Basically speak- 
ing, it is a matter of replacing the toolbit with the 
toolpost grinder and computing feeds and speeds 
for grinding instead of planing. Prior to 
attempting surface grinding on the planer, be sure 
you have a thorough understanding of the 
material presented in chapter 13 of this manual. 

When you have completed the grinding job, 
you must clean the planer extensively, both 
inside and out. Filter or change the oil in the 
hydraulic system prior to further operation. The 



PANTOGRAPHS 

The pantograph (engraving machine) is 
essentially a reproduction machine. It is used in 
the Navy for work such as engraving letters and 
numbers on label plates, engraving and graduating 
dials and collars, and in other work that requires 
the exact reproduction of a flat pattern on the 
workpiece. The pantograph may be used for 
engraving flat and uniformly curved surfaces. 

There are several different models of en- 
graving machines that you may have to operate. 
Figure 12-18 shows one model that mounts on a 
bench or a table top and is used primarily for 
engraving small items. This particular machine is 
manufactured by the New Hermes Engraving 
Machine Corporation. It is capable of reproduc- 
ing work at ratios ranging from 1:1 to 7:1. A 1 
to 1 ratio will result in the work being 1/7 the size 
of the pattern. 



B. CONICAL POINT; 
SCREW 





C,D,E, AND F EXTENSION BASES 




28.332 



Figure 12-18. Engraving machine. 



12-17 



The Gorton 3-U pantograph (figure 12-19) is 
another engraving machine commonly used by the 
Navy. The principles of operation and setup 
procedures for the 3-U machine are similar to 
those for other models of pantograph type engrav- 
ing machines. Because of the similarity in 
operating principles and setup procedures, you 
should have no difficulty in applying the 
information contained in this section to the 
operation of any model of pantograph engraver. 



PANTOGRAPH ENGRAVER UNITS 

The pantograph engraving machine, shown in 
figure 12-19, consists of five principal parts: the 
supporting base, pantograph assembly, cutterhead 
assembly, worktable, and copyholder. 

Supporting Base 

The supporting base is a heavy, rigid casting, 
which supports the entire piece of machinery. If 



CONNECTING 
LINK 



COPY- 
HOLDER 



TRACER ARM 
I 
END BOSS 



LOWER BAR 



FORMING BAR 



FORMING GUIDE 



CUTTERHEAD 
ASSEMBLY 



WORKTABLE 



CROSSFEED 
CONTROL 



TRANSVERSE 
FEED 



VERTICAL FEED 
CONTROL 




<\ 



Gorton Pantographs made by FAMCO Machine since 1988 



1 UUJ.VJ V CU. 1J.V7JL11 Lilt 



on rubber or cork pads. 
Pantograph Assembly 

The pantograph assembly has four connecting 
arms: a tracer arm, an upper bar, a lower bar, 
and a connecting link between the tracer arm and 
the lower bar. It also has a cutterhead link which 
supports the cutterhead. The relationship between 
movement of the stylus point and movement of 
the cutter is governed by the relative positions of 
the sliding blocks on the upper bar and the lower 
bar. The pantograph assembly can be set for a 
given reduction by loosening the sliding block 
bolts and setting the blocks at a desired distance 
from the datum lines. This will give the desired 
reduction ratio. The upper and lower bar are 
inscribed with marks (for whole number and 
standard reductions from 2:1 to 16: 1) to indicate 
the position for setting the slider blocks for 
commonly used reductions. 

Cutterhead Assembly 

The cutterhead assembly houses the precision 
cutter spindle. Pulley drives between the motor 
and the spindle enable you to adjust the spindle 
speeds. Figure 12-20 gives the spindle speeds and 
the arrangement of the drive belts for varying 
spindle speeds. At the head of the cutter there is 
a vertical feed lever, which provides a range of 
limited vertical movement from 1/16 inch to 1/4 
inch to prevent the cutter from breaking when it 
feeds into work. A plunger locks the spindle for 
flat surface engraving or releases it for floating 



MOTOR DRIVE SPINDLE 
2 l 

HJ BS: ^^ 


2-3-A-C 3800 rpm 
2-3-A-D 5300 rpm 
1-3-A-C 5300 rpm 
1-3-A-D 7400 rpm 


2-3 -B-C 8100 
2-3-B-D 11,000 

1-3-B-C 11,000 
1-3-B-D I5POO 


rpm 

rpm 

rpm 
rpm 



Gorton Pantographs made by FAMCO Machine since 1988 

28.235X 
Figure 12-20. Spindle speeds. 



. . . . . . , 

making it unnecessary to disturb any work by 
lowering the table. 



Worktable 

The cast iron worktable of the 3-U pantograph 
engraver measures 8 inches by 12 inches and is 
flat and highly polished. It has four 3/8-inch 
T-slots cut parallel to its front edge for mounting 
a vise or table dogs to hold down a piece of work. 
Longitudinal feed can move the worktable 10 
inches, while the cross feed can move the table 
1 1 inches. Vertical feed of the worktable is 9 3/4 
inches. 



Copyholder 

The copyholder is a steel casting with beveled 
grooves or T-slots machined from the solid plate 
holder. Standard copyholders for the 3-U 
pantograph engravers have four or six grooves. 
Two stops are supplied for each groove in the 
copyholder. 



SETTING COPY 

Lettering used with an engraver is known by 
various terms however, the Navy uses the term 
copy to designate the characters used as sample 
guides. Copy applies specifically to the standard 
brass letters, or type, which are set in the 
copyholder of the machine and which guide 
the pantograph in reproducing. Shapes, as 
distinguished from characters, are called templates 
or masters. 

Copy is not self-spacing; therefore, you should 
adjust the spaces between the characters by 
inserting suitable blank spacers, which are 
furnished with each set of copy. Each line, when 
set in the copyholder, should be held firmly 
between the clamps. 

After setting up the copy in the holder, and 
before engraving, be sure that the holder is firmly 
set against the stop screws in the copyholder base. 
This ensures that the holder is square with the 
table. Do not disturb these stops; they were 
properly adjusted at the factory, and any change 
will throw the copyholder out of square with the 
table. The worktable T-slots are parallel with the 
table's front edge, making it easy to set the work 
and the copy parallel to each other. 



12-19 



In addition to copy, circular copy plates are 
sometimes used for engraving work. A copy plate 
is a flat disk with letters, numbers, and other 
characters inscribed on the face of the disk near 
the rim. The rim of the plate is notched beside 
each character so a spring-loaded indexing pawl 
can be used to hold the disk in the proper position 
during the engraving procedure. The plate is 
set on a pivot on the copyholder and may be 



rotated 360 so that any character on the 
plate may be placed in the required position for 
engraving. 



SETTING THE PANTOGRAPH 

The correct setting of the pantograph is 
determined from the ratio of (1) the size of the 




\ 20.0390' . 
\5Od . 990 ^ 



' 

\J23 . 





CONSTANT 

?54 .495/rr r> 
Upper 3ar Consent -, 



, 
Centers. 



U^7Lj/*<^^ 

7450" + 3 fir*/, teuton +j). Loner for Cans f art? =^eJ .039 o'+ 



EXAMPLE: REQUIRED THE SETTINGS IN INCHES FOR REDUCING 4 TO I. 



For 




4. 0)2O.O39O' 
/* 5.0097' 

Tracer drm. .. 

Centers. 



D/srance fo set Me* cfye or? Lowes' 



S/der Bar .leatf from 
See 



S//der ffar. 



first d/^e Me Upper S/tfer Sar Ce/ifer d/s - 
torrce /Z.7450' ty tic Deduction 
fas <y cor, >s ;/?/?/ of /. 

Upper S//cfer Bar Centers. 
.4.O ^ 



Upper 




2.5489' 



Subfract /rom^4.2'483'- 
"~" 



Distance - - / .6994' 

h je/ /ndtx Edye or/ Upper Steer Bar 

from (5r<x7t/fff/or/ <?. 5ee~ 



PANTOGRAPH 
SET TO THE 
REDUCTION. 



4.0 




To 



for ar/f/ desired 
Spec /a/ Sc&Se a/ tfe- 
as per <?6ove 
or as per" Sd?edu/e o/ 



Ptece Me 3eve//ed /rttfex 
of Me <5Aderj awfft/ /ro/n 
fhe L/sies morAec/ J? or/ Me 
Bars, She O/s forces 



4.O 



fike Lower Sti^tf 
be se/ es a/ & 5.O/O' 
from She U'rre ^ asx? Sfte 
i/pper 5//der ff/ocA as a/ 
1.699' from its Line 2. 



Gorton Pantographs made by FAMCO Machine since 1988 



work to the size of the copy layout, or (2) the 
desired size of engraved characters to the size of 
the copy characters. This ratio is called a 
reduction. A 1:1 reduction results in an engraved 
layout equal in size to the copy layout; a 16:1 
reduction results in an engraved layout 1/16 the 
size of the copy layout. 

If a length of copy is 10 inches and the length 
of the finished job is to be 2 inches, divide the 
length of the job into the length of the copy: 

10 *- 2 = 5 inches 
For this job, set the slider blocks at 5 inches. 

If the length of the copy is 1 1 inches and the 
length of the finished job is to be 4 inches, the 
reduction is: 

11 -* 4 = 2.75 inches 

You will note that reduction 2.75 is not marked 
on the pantograph bars. To find the correct slider 
blocks settings, use the reduction formula in 
figure 12-21. 

All settings are measured from the first 
reduction marking on the upper and lower arms. 
On the model 3-U pantograph, reductions are 
measured from the line marked 2 on the upper 



arm, and NOT the line marked 1. To accurately 
set special reductions use a hundredth-inch 
scale. 

After you have set a special reduction, check 
the pantograph. First, place a point into the 
spindle, then raise the table until the point barely 
clears the table. Next, trace along an edge of a 
copy slot in the copyholder with the tracing stylus. 
If the cutter point follows parallel to the T-slots, 
the reduction is proper. If the point forms an arc 
or an angle, recalculate the setting and reset the 
sliding blocks. If the point still runs off, loosen 
either of the slider blocks and tap it one way or 
the other, until the path of the point is parallel 
to the T-slots. 

For 1:1 reduction, transfer the stylus collet 
from the end boss of the tracer arm to the second 
boss on the arm. Set the lower slider block on the 
graduation marked "1 and 2," and the upper bar 
slider block on graduation 1. 

Table 12-2 provides dimensions for setting the 
slider blocks on the upper and lower bars for 
reductions 2 through 16. After setting the 
reduction, lock the upper and lower bars in the 
slider blocks by tightening the capscrews in each 
block. 

NOTE: For special reductions between 
1 and 2, follow the sample solution in 
fig. 12-22. 



TRACER ARM 
10.0195" 

v 




EXAMPLE 

REQUIRED: THE SETTING IN INCHES FOR REDUCING 



1.5 TO I 



FOR LOWER SLIDER BAR 

STEP1, DIVIDE TRACER ARM CENTERS BY THE 
REQUIRED REDUCTION THUS! 
TRACER ARM CENTERS 10.0195" 
REQUIRED REDUCTION 1.5 = 6 ' 679 
STEP2. SUBTRACT THE QUOTIENT FROM THE LOWER 
BAR CONSTANT. 10.0195" 
- 6.679" 



STEP3. 



3.340" 

THE RESULT IS THE DISTANCE TO SET INDEX 
EDGE ON LOWER SLIDER BAR HEAD FROM 
GRADUATION 182. 



FOR UPPER SLIDER BAR 
DIVIDE UPPER SLIDER BAR CENTER 
DISTANCE BY THE REDUCTION REQUIRED 
PLUS A CONSTANT OF ONE. 
REQUIRED REDUCTION 1.5 
CONSTANT 1,0 
2.5 
UPPERSLIDERBAR CENTERS 12.745", 



2.5 



5.098 



STEP2. SUBTRACT THE QUOTIENT FROM THE 

UPPER BAR CONSTANT .3725" 
STEP3. THE RESULT IS THE - 5.098 " 

DISTANCE TO SET 1.2745" 

INDEX EDGE ON UPPER 

SLIOER 8A.RHEA.D FROM GRADUATION I. 



SCHEDULE OF VARIOUS REDUCTIONS 
BETWEEN l:l AND 2:1 ON MOD. 3U 
PANTOGRAPH WITH TRACING STYLUS 
IN NEAREST HOLE OF ARM. 


MEASUREMENTS IN INCHES 


REDUCTION 


DISTANCE TO SET 
INDEX EDGE ON 
LOWER SLIDER BAR 
HEAD FROM GRAD. 
MARKS 1 & Z 


DISTANCE TO SET 
INDEX EDGE ON 
UPPER SLIDER BAR 
HEAD FROM GRAD. 
MARK 1 


.0 
. 1 
,2 
.3 
,4 
.5 
.6 
.7 
.8 
.9 



.911" 
1.670" 
2.3 1 2" 
2.863" 
3.340" 
3.757" 
4. 1 2 6" 
4.453" 
4.746" 



,303" 
.579" 
.83 1 ' 
,062" 
275" 
,471 " 
,651" 
.82 l" 
1.978 


FOR OTHER REDUCTIONS USE FORMULA 


FOR GREATER REDUCTIONS USE SCHEDULE 
AS PER NSTRUCTION BOOK WITH TRACING 
STYLUS ATEXTREME END OF PANTOGRAPH ARM 



Gorton Pantographs made by FAMCO Machine since 1988 



Engraving Machine No. 3U 




Engraving Machine No. 3U 


Reduction 


Lower Bar 
Inches 


Upper Bar 
Inches 




Reduction 


Lower Bar 
Millimeters 


Upper Bar 
Millimeters 


2.0 


0.000 


0.000 


2.0 


00.00 


0.00 


2.1 


0.477 


0.137 


2.1 


12.12 


3.48 


2.2 


0,911 


0.265 


2.2 


23.14 


6.74 


2.3 


1.307 


0.386 


2.3 


33.19 


9.81 


2.4 


1.670 


0.500 


2.4 


42.42 


12.69 


2.5 


2.004 


0.607 


2.5 


50.90 


15.41 


2.6 


2.312 


0.708 


2.6 


58.73 


17.98 


2.7 


2.598 


0.804 


2.7 


65.98 


20.41 


2.8 


2.863 


0.894 


2.8 


72.71 


22.72 


2.9 


3.109 


0.980 


2.9 


78.98 


24.90 


3.0 


3.340 


1.062 


3.0 


84.83 


26.98 


3.1 


3.555 


1.140 


3.1 


90.30 


28.95 


3.2 


3.757 


1.214 


3.2 


95.44 


30.83 


3.3 


3.947 


1.284 


3.3 


100.26 


32.62 


3.4 


4.126 


1.352 


3.4 


104.79 


34.33 


3.5 


4.294 


1.416 


3.5 


109.07 


35.97 


3.6 


4.453 


1.478 


3.6 


113.11 


37.53 


3.7 


4.604 


1.537 


3.7 


116.93 


39.03 


3.8 


4.746 


1.593 


3.8 


120.55 


40.46 


3.9 


4.881 


1.647 


3.9 


123.98 


41.84 


4.0 


5.010 


1.699 


4.0 


127.25 


43.16 


4.1 


5.132 


1.749 


4.1 


130.35 


44.43 


4.2 


5.248 


1.797 


4.2 


133.31 


45.65 


4.3 


5.359 


1.844 


4.3 


136.13 


46.83 


4.4 


5.465 


1.88,8 


4.4 


138.82 


47.96 


4.5 


5.566 


1.931 


4.5 


141.39 


49.05 


4.6 


5.663 


1.972 


4.6 


143.84 


50,10 


4.7 


5.756 


2.012 


4.7 


146.20 


51.11 


4.8 


5.845 


2.051 


4.8 


148.46 


52.09 


4.9 


5.930 


2.088 


4.9 


150.62 


53.04 


5.0 


6.012 


2.124 


5.0 


152.70 


53.95 


5.1 


6.090 


2.159 


5.1 


154.69 


54.84 


5.2 


6.166 


2.193 


5.2 


156.61 


55.69 


5.3 


6.239 


2.225 


5.3 


158.46 


56.52 


5.4 


6.309 


2.257 




5.4 


160.24 


57.33 



Gorton Pantographs made by FAMCO Machine since 1988 



28.236.01X 



12-22 



Table 12-2. Reduction Schedules in Inches and Millimeters Continued 



Schedule of Reductions for 
Engraving Machine No. 3U 




Schedule of Reductions for 
Engraving Machine No. 3U 


Reduction 


Lower Bar 
Inches 


Upper Bar 
Inches 




Reduction 


Lower Bar 
Millimeters 


Upper Bar 
Millimeters 


5.5 


6.376 


2.288 




5.5 


161.95 


58.10 


5.6 


6.441 


2.317 




5.6 


163.60 


58.86 


5.7 


6.504 


2.346 




5.7 


165.20 


59.59 


5.8 


6.564 


2.374 




5.8 


166.74 


60.30 


5.9 


6.623 


2.401 




5.9 


168.23 


60.99 


6.0 


6.680 


2.428 




6.0 


169.66 


61.66 


6.1 


6.734 


2.453 




6.1 


171.05 


62.31 


6.2 


6.787 


2.478 




6.2 


172.40 


62.95 


6.3 


6.839 


2.502 




6.3 


173.70 


63.56 


6.4 


6.888 


2.526 




6.4 


174.97 


64.16 


6.5 


6.937 


2.549 




6.5 


176.19 


64.74 


6.6 


6.983 


2.571 




6.6 


177.38 


65.31 


6.7 


7.029 


2.593 




6.7 


178.53 


65.87 


6.8 


7.073 


2.614 




6.8 


179.64 


66.40 


6.9 


7.115 


2.635 




6.9 


180.73 


66.93 


7.0 


7.157 


2.655 




7.0 


181.78 


67.44 


7.1 


7.197 


2.673 




7.1 


182.81 


67.94 


7.2 


7.236 


2.694 




7.2 


183.80 


68.43 


7.3 


7.274 


2.713 




7.3 


184.77 


68.90 


7.4 


7.312 


2.731 


7.4 


185.71 


69.37 


7.5 


7.348 


2.749 


7.5 


186.63 


69.82 


7.6 


7.383 


2.766 




7.6 


. 187.32 


70.26 


7.7 


7.417 


2.783 




7.7 


188.39 


70.70 


7.8 


7.450 


2.800 




7.8 


189.24 


71.12 


7.9 


7.483 


2.816 




7.9 


190.07 


71.53 


8.0 


7.515 


2.832 




8.0 


190.87 


71.94. 


9.0 


7.793 


2.974 


9.0 


197.94 


75.53 


10.0 


8.016 


3.090 


10.0 


203.60 


78.48 


11.0 


8.198 


3.186 


11.0 


208.22 


80.93 


12.0 


8.350 


3.268 


12.0 


212.08 


83.01 


13.00 


8.478 


3.338 


13.0 


215.34 


84.78 


14.00 


8.588 


3.399 


14.0 


218.13 


86.32 


15.00 


8.683 


3.452 


15.0 


220.56 


87.67 


16.00 


8.767 


3.499 


16.0 


222.68 


88.86 



Gorton Pantographs made by FAMCO Machine since 1988 



28.236.01X 



CUTTER SPEEDS 



GRINDING CUTTERS 



The speeds listed in table 12-3 represent typical 
speeds for given materials. In using the table, keep 
in mind that the speeds recommended will vary 
greatly, depending on the depth of cut, and 
particularly the rate at which you feed the cutter 
through the work. Since the 3-U engravers are fed 
manually, the rate of feed is subject to a wide 
variation by individual operations; this will affect 
the spindle speeds used. 

Run the cutters at highest speeds possible 
without burning them, and remove stock with 
several light, fast cuts rather than one heavy cut 
at slower spindle speeds. When you cut steel and 
other hard materials, start with a slow speed and 
work up to the fastest speed the cutter will stand 
without losing its cutting edge. Sometimes you 
may have to sacrifice cutter life to obtain the 
smoother finish possible at higher speeds. With 
experience you will know when the cutter is 
running at its maximum efficiency. 



Most of the difficulties experienced in using 
very small cutters on small lettering are caused by 
improper grinding. The cutter point must be accu- 
rately sharpened. When trouble is experienced, 
usually the point is burned, or the flat is either 
too high or too low. Perhaps the clearance does 
not run all the way to the point. Stoning off the 
flat with a small fine oilstone will make the 
cutting edge keener. 

You can make a cutter run almost perfectly 
by sharpening it in the spindle in which it will run. 
Most pantograph machines have a provision for 
removing the cutter spindle from the machine and 
placing it in a V-block toolhead on the cutter 
grinder. This will allow you to grind the cutter 
to the desired shape without removing it from the 
cutter spindle. 

Grinding Single-Flute Cutters 

Before grinding cutters, true up the grinding 
wheel with the diamond tool supplied with the 



Table 12-3. Cutter Speeds 



Materials and Feeds 


Cutter diameter (at cutting point) 


1/32" 


1/16" 


1/8" 


3/16" 


1/4" 


5/16" 


3/8" 


7/16" 


1/2" 


Speeds (rpm) 


Hardwood (650-800 ft. /min. ) 


10,000 
to 
20,000 


10,000 
to 
20,000 


10,000 
to 
20,000 


10,000 
to 
20,000 


10,000 
to 
20,000 


9,000 


8,000 


7,000 


6,000 


*Bakelite (170-250 ft. /min. ) 


10,000 


8,000 


6,000 


4,000 


3,000 


2,200 


1,800 


1,500 


1.300 


**Engraver's brass and 
aluminum (375-425 ft. /min. ) 


10,000 
to 

15,000 


10,000 
to 
15,000 


10,000 
to 
15,000 


8,000 


6,000 


5,000 


4,000 


3,500 


3,000 


Cast iron (130-250 ft. /min. ) 


8,000 


7,500 


5,500 


3,500 


2,500 


2,000 


1,650 


1.400 


1,200 


Hard bronze and machine steel 
(80-200 ft. /min. ) 


7,000 


6,000 


3,000 


2,200 


1,600 


1,200 


975 


800 


700 


Annealed tool steel (70-100 ft. / 
min. ) 


5,000 


4.500 


2,300 


1,600 


1,200 


1,000 


850 


725 


600 


Stainless steel, Monel (45-75 
ft. /min. ) 


3,500 


2,750 


1,400 


1,050 


700 


575 


500 


435 


350 


Very hard die and alloy steels 
(30-45 ft./min.) 


2.000 


1,250 


800 


600 


475 


400 


350 


300 


250 



the wheel as shown in figure 12-23. Then swing 
the diamond across the face of the wheel by 
rocking the toolhead in much the same manner 
as for grinding a cutter. In dressing the wheel, 
your maximum cut should be 0.001 to 0.002 inch. 
If the diamond fails to cut freely, turn it slightly 
in the toolhead to present an unused portion of 
the diamond to the wheel. 

ROUGH AND FINISH GRINDING A 
CONICAL POINT. Set the grinder toolhead to 
the desired cutting edge angle (fig. 12-24 A). This 
angle usually varies from 30 to 45 , depending 
on the work desired. For most sunken letter or 
design engraving on metal or bakelite plates, a 30 
angle is used. Now place the cutter in the toolhead 
and rough grind it to approximate size by swinging 
it across the wheel's face. Do not rotate the cutter 
while it is in contact with the face of the wheel 
but swing it straight across, turning it slightly 
BEFORE or AFTER it makes contact with the 
wheel. This will produce a series of flats as in 
figure 12-24B. Now, grind off the flats and 
produce a smooth cone by feeding the cutter into 
the wheel and rotating the cutter at the same time. 
The finished cone should look like figure 12-24B, 
smooth and entirely free of wheel marks. 



l,v/ gJ.llJ.Vl L11V/ lldl. 




SIC 



Y"V"7: 

JSi 



Gorton Pantographs made by FAMCO Machine since 1988 

28.238X 

Figure 12-23. Position of diamond for truing a grinding 
wheel. 





Gorton Pantographs made by FAMCO Machine since 1988 

28.239X 

Figure 12-24. Grinding a conical point: (A) Cutter angle. 
(B) Rough and finished conical shape. 



For very small, delicate work it is absolutely 
essential to grind this flat EXACTLY to center. 
If the flat is oversize, you can readily see it after 
grinding the cone, and the point will appear as 
in figure 12-25 A. To correct this, grind the flat 
to center as in figure 12-25B. 

GRINDING THE CHIP CLEARANCE. 

The cutter now has the correct angle and a 
cutting edge, but has no chip clearance. This must 
be provided to keep the back side of the cutter 
from rubbing against the work and heating 
excessively, and to allow the hot chips to fly off 
readily. The amount of clearance varies with the 
angle of the cutter. The procedure for grinding 
chip clearance is as follows. 

Gently feed the cutter into the face of the 
wheel. Do not rotate the cutter. Hold the back 
(round side) of the conical point against the wheel. 
Rock the cutter continuously across the wheel's 
face, without turning it, until you grind a flat that 
runs out exactly at the cutter point (fig. 12-26). 
Check this very carefully, with a magnifying glass 




\ 



Gorton Pantographs made by FAMCO Machine since 1988 

28.240X 

Figure 12-25. Grinding the flat. (A) Flat not ground to 
center. (B) Flat ground to center. 



CUTTING EDGE 




BACK SIDE 
OF CUTTER 



Gorton Pantographs made by FAMCO Machine since 1988 

28.241X 
Figure 12-26. First operation in grinding clearance. 



12-25 



if necessary, to be sure you have reached the point 
with this flat. Be extremely careful not to go 
beyond the point. 

The next step is to grind away the rest of the 
stock on the back of the conical side to the angle 
of the flat, up to the cutting edge. Rotate the 
conical side against the face of the wheel and 
remove the stock as shown in figure 12-24B. Be 
extremely careful not to turn the cutter too far 
and grind away part of the cutting edge. Clean 



up all chatter marks. Be careful of the point; this 
is where the cutting is done. If this point is 
incorrectly ground, the cutter will not work. 

TIPPING OFF THE CUTTER POINT. For 

engraving hairline letters up to 0.0005 inch in 
depth, the cutter point is not flattened, or 
TIPPED OFF. For all ordinary work, however, 
it is best to flatten this point as much as the work 
will permit. Otherwise, it is very difficult to 
retain a keen edge with such a fine point, and 



Table 12-4. Rake Angles for Single-Flute Cutters 



Material to be cut 


Angle B (See figs. 
12-27).andl2-28j 




- 5-10 degrees 
10-15 degrees 
15-20 degrees 
20-25 degrees 
20-25 degrees 













Table 12-5. Chip Clearance Table for Square-Nose Cutters 



Cutter diameter 


Clearance 


Cutter diameter 


Clearance 


Inches 


Inches 


Inches 


Inches 


1/10 


.004 


1/4 


.010 


1/8 


.006 


5/16 


.012 


5/32 


.006 


3/8 


.015 


3/16 


.008 


7/16 


.015 






1/2 


.020 



Table 12-6. Clearance Angles for 3- and 4-Sided Cutters 



Degrees of cutting ....... 


45 


40 


35 


30 


25 


20 


15 


10 


5 






















Angle of clearance: (Degrees) 




















3 sides 


26 1/2 


23 


19 1/2 


16 


13 


10 1/2 


7 1/2 


5 


21/2 
























35 1/2 


23 


25 1/2 


22 1/2 


18 1/2 


14 1/2 


10 


7 


3 1/2 























when the point wears down, the cutter will 
immediately fail to cut cleanly. Tipping off is 
usually done by holding the cutter in the hands 
at the proper inclination from the grinding wheel 
face and touching the cutter very lightly 
against the wheel, or by dressing with an oilstone. 
Angle A (fig. 12-27) should be approximately 3 ; 
this angle causes the cutter to bite into the work 
like a drill when it is fed down. Angle B (fig. 
12-27) varies, depending on the material to be 
engraved. Use table 12-4 as a guide in determining 
angle B. 

Grinding Square-Nose 
Single-Flute Cutters 

A properly ground square-nose single-flute 
cutter should be similar to the illustration in 



WIDE AS POSSIBLE 





af 



SEE 

TABLE 

12-4 



figure 12-28. When square-nose cutters are 
ground, they should be tipped off in the 
same manner as described in connection with 
figure 12-27. All square-nose cutters have 
peripheral clearance ground back of the cutting 
edge. After grinding the flat to center (easily 
checked with a micrometer), grind the clearance 
by feeding the cutter in the required amount 
toward the wheel and turning the cutter until you 
have removed all stock from the back (round 
side), up to the cutting edge. Table 12-5 provides 
information on chip clearance for various sized 
cutters. 



Grinding Three- and 
Four-Sided Cutters 

Three- and four-sided cutters (see fig. 12-29) 
are used for cutting small steel stamps and for 
small engraving where a very smooth finish is 
desired. The index plate on the toolhead collet 
spindle has numbered index holes for indexing to 
grind three-and four-sided cutters. 

Set the toolhead for the desired angle. Plug 
the pin in the index hole for the desired number 
of divisions and grind the flats. Now, without 
loosening the cutter in the toolhead collet, reset 
the toolhead to the proper clearance angle. 
Clearance angles are listed in table 12-6. 



Gorton Pantographs made by FAMCO Machine since 1988 

28.242X 
Figure 12-27. A tipped off cutter. 



SEE TABLE 12-4 






Gorton Pantographs made by FAMCO Machine since 1988 

28.243X 

Figure 12-28. Square-nose cutter with a properly ground 
tip. 



PANTOGRAPH ATTACHMENTS 

Some attachments commonly used with the 
pantograph engraving machine are: copy dial 
holders, indexing attachments, forming guides 
and rotary tables. The use of these attachments 
extends the capabilities of the pantograph 
engraving machine from flat, straight line 
engraving to include circular work, cylindrical 
work, and indexing. 




Gorton Pantographs made by FAMCO Machine since 1988 

28.244X 
Figure 12-29. Three-sided cutter. 




Gorton Pantographs made by FAMCO Machine since 1988 



28.245X 



Figure 12-30. Copy dial bolder and plate. 



The copy dial holder shown in figure 
12-30 is used instead of the regular copy- 
holder when a circular copy plate is used. 
This holder has a spring-loaded indexing 
pawl, which is aligned with the center pivot 
hole. This pawl engages in the notches in 
a circular copy plate to hold the plate in 
the required position for engraving the character 
concerned. 

An indexing attachment such as that shown 
in figure 12-31 may be used for holding cylindrical 
work to be graduated. In some cases, the dividing 
head (used on the milling machine) is used 
for this purpose. The work to be engraved 




Gorton Pantographs made by FAMCO Machine since 1988 



18 



for any number of divisions available on 
the plate. Figure 12-31 shows a micrometer 
collar being held for graduation and engrav- 
ing. 

A forming guide (sometimes called a radius 
plate) is used to engrave cylindrical surfaces. The 
contour of the guide must be the exact opposite 
of the work; if the work is concave the guide must 
be convex and vice versa. The forming guide is 
mounted on the forming bar. (See fig. 12-32.) 
When the spindle floating mechanism is released, 
the spindle follows the contour of the forming 
guide. 

The rotary table shown in figure 12-32 
is used for holding work such as face dials. 
It is similar to the rotary table used on 
milling machines. The rotary table is mounted 
directly on the worktable and provides a 
means of rapid graduation and of engraving the 
faces of disks. 



USING A CIRCULAR 
COPY PLATE 

The circular copy plate might be efficiently 
used in engraving a number of similar workpieces 
with single characters used consecutively. For 
example, the following setup can be used to 
engrave 26 similar workpieces with a single 




letter. 

1. Set the workpiece conveniently on the 
worktable and clamp two aligning stops in place. 
These stops will not be moved until the entire job 
is completed. 

2. Set the circular plate on the copyholder so 
that the plate can be rotated by hand. Check to 
ensure that the indexing pawl engages the notch 
on the rim so the plate will be steady while you 
trace each character. 

3 . Set the machine for the required reduction 
and speed, and adjust the worktable so the spindle 
is in position over the workpiece. 

4. Clamp the first workpiece in place on the 
worktable. (The aligning stops, step 1, ensure 
accurate positioning.) 

5. Rotate the circular plate until the letter A 
is under the tracing stylus and the index pawl is 
engaged in the notch. 

6. Engrave the first piece with the letter A. 
Check the operation for required adjustments of 
the machine. 

7. After you have finished the first piece, 
remove it from the machine. Do not change the 
alignment of the aligning stops (step 1), the 
worktable, or the copyholder. Place the second 
workpiece in the machine. Index the circular plate 
to the next letter and proceed as previously 
described. 

8. Continue loading the workpieces, indexing 
the plate to the next character, engraving, and 
removing the work, until you have finished the 
job. 



ENGRAVING A GRADUATED 
COLLAR 

To engrave a graduated collar, as shown in 
figure 12-31, use a forming guide and indexing 
attachment. You can also use the circular copy 
plate to speed up the numbering process. After 
you have engraved each graduation, index the 
work to the next division until you have finished 
the graduating. When you engrave numbers with 
more than one digit, offset the work angularly by 
rotating the work so the numbers are centered on 
the required graduation marks. 



Gorton Pantographs made by FAMCO Machine since 1988 

28.247X 
Figure 12-32. A rotary table. 



ENGRAVING A DIAL FACE 

Use a rotary table and a circular copy plate 
to engrave a dial face, such as the one shown in 



12-29 



figure 12-33. Note that the figures on the right 
side of the dial are oriented differently from 
those on the left side; this illustrates the usual 
method of positioning characters on dials. The 
graduations are radially extended from the center 
of the face. The graduations also divide the dial 
into eight equal divisions. 

To set up and engrave a dial face, proceed as 
follows: 

1 . Set the reduction required. The size of the 
copy on the circular copy plate and the desired 
size of numerals on the work are the basis for 
computing the reduction. 

2. Set the copy plate on the copyholder, 
ensuring that it is free to rotate when the ratchet 
is disengaged. 

3 . Mount a rotary table on the worktable of 
the engraver. Position the dial blank on the rotary 
table so the center of the dial coincides with the 
center of the rotary table. Clamp the dial blank 
to the rotary table. 

4. Place the tracing stylus in the center of the 
circular copy plate and adjust the worktable so 
the center of the dial is directly under the point 
of the cutter. 




Figure 12-33. A dial face. 



5. Rotate the copy plate until the copy 
character for making graduation marks is aligned 
with the center of the copy plate and the center 
of the work. Set the stylus in this mark. Now, by 
feeding the worktable straight in toward the back 
of the engraver, adjust the table so the cutter will 
cut the graduation to the desired length. 

6. Start the machine and adjust the engraver 
worktable vertically for the proper depth of cut. 
Then clamp the table to prevent misalignment of 
the work. Any further movement of the work will 
be made by the rotary table feed mechanism. 

7. Engrave the first graduation mark. 

8. Using the rotary table feed wheel, rotate 
the dial to the proper position for the next 
graduation. As there are eight graduations, rotate 
the table 45 ; engrave this mark and continue until 
the circle is graduated. You will now be back to 
the starting point. 

NOTE: Do not move the circular copy plate 
during the graduating process. 

9. To engrave numbers positioned as shown 
on the right side of the dial in figure 12-33, move 
the worktable so the cutter is in position for 
engraving the numbers. Rotate the circular copy 
plate to the numeral 1 and engrave it. Rotate the 
rotary table 45 and the circular copy plate to 2, 
and engrave. Continue this process until you have 
engraved all the numbers. If two (or more) digit 
numbers are required, offset the dial as previously 
described. 

10. To engrave the numbers shown on the left 
side of the dial in figure 12-33, rotate the copy 
plate to the required number and then, using the 
cross feed and longitudinal feed of the engraver 
table, position the cutter over the work at the 
point where the number is required. This method 
requires that the worktable be repositioned for 
each individual number. As previously stated, 
movement of the engraver worktable in two 
directions results in angular misalignment of the 
character with the radius of the face; in this 
example, angular misalignment is required. 



PRECISION GRINDING MACHINES 



Modern grinding machines are versatile and 
are used to perform work of extreme accuracy. 
These machines are used primarily for finishing 
surfaces that have been machined in other 
machine tool operations. Surface grinders, 
cylindrical grinders, and tool and cutter grinders, 
installed in most repair ships, can perform 
practically all of the grinding operations required 
in Navy repair work. 

A Machinery Repairman must demonstrate an 
ability to: (1) mount, dress, and true grind 
machine wheels; (2) perform precision grinding 
operations using a magnetic chuck; (3) grind cutter 
tool bits on a surface grinder for Acme and square 
threading; and (4) set up and grind milling cutters 
using a tool and cutter grinder. 

To perform these jobs, you must have a 
knowledge of the construction and principles of 
operation of commonly used grinding machines. 

You gain proficiency in grinding through 
practical experience. Therefore, you should take 
every available opportunity to watch or perform 
grinding operations from setup to completion. 

There are several classes of each type of 
grinder. The SURFACE grinder may have either 
a rotary or a reciprocating table, and either a 
horizontal or vertical spindle. Cylindrical grinders 
may be classified as plain, centerless, or internal 
grinders. The tool and cutter grinder is basically 
a cylindrical grinder. Grinders generally found in 
the shipboard machine shop are the reciprocating 
table, horizontal spindle (planer type), surface 
grinder; the plain cylindrical grinder; the tool and 
cutter grinder; and sometimes a universal grinder. 
The universal grinder is similar to a tool and 
cutter grinder except that it is designed for heavier 
work and usually has a power feed system and 
a coolant system. 

Before operating a grinding machine, you 
must understand the underlying principles of 
grinding and the purpose and operation of the 
various controls and parts of the machine. You 
must also know how to set up the work in the 
machine. The setup procedures will vary with the 



different models and types of machines. 
Therefore, you must study the manufacturer's 
technical manual to learn specific procedures for 
using a particular model of machine. 



SPEEDS, FEEDS, AND COOLANTS 

As with other machine tools, the selection of 
the proper speed, feed, and depth of cut is an 
important factor in successful grinding. Also, the 
use of coolants may be necessary for some 
operations. The definitions of the terms speed, 
feed, and depth of cut, as applied to grinding, are 
basically the same as for other machining 
operations. 

INFEED is the depth of cut that the wheel 
takes in each pass across the work. TRAVERSE 
(longitudinal or cross) is the rate that the work 
is moved across the working face of the grinding 
wheel. WHEEL SPEED, unless otherwise 
defined, means the surface speed in fpm of the 
grinding wheel. 

WHEEL SPEEDS 

Grinding wheel speeds commonly used in 
precision grinding vary from 5,500 to 9,500 fpm. 
You can change wheel speed by changing the 
spindle speed or by using a larger or smaller wheel. 
To find the wheel speed in fpm, multiply the 
spindle speed (rpm) by the wheel circumference 
(inches) and divide the product by 12. 

fpm - (cir - * 2 rpm) 



fpm = 



rpm 






The maximum speed listed on grinding wheels 
is not necessarily the speed at which the wheel will 
cut best. The maximum speed is based on the 



13-1 



strength of the wheel and provides a margin of 
safety. Usually, the wheel will have better cutting 
action at a lower speed than that listed by the 
manufacturer as a maximum speed. 

One method of determining the proper wheel 
speed is to set the wheel speed between the 
minimum and maximum speeds recommended by 
the wheel's manufacturer. Take a trial cut. If the 
wheel acts too soft (wears away too fast), increase 
the speed. If the wheel acts too hard (slides over 
the work or overheats the work), decrease the 
speed. 

TRAVERSE (WORK SPEED) 

During the surface grinding process, the work 
moves in two directions. As a flat workpiece is 
being ground (fig. 13-1), it moves under the 
grinding wheel from left to right (longitudinal 
traverse). The speed at which the work moves 
longitudinally is called work speed. The work also 
moves gradually from front to rear (cross 
traverse), but this movement occurs at the end of 
each stroke and does not affect the work speed. 
The method for setting cross traverse is discussed 
later in this chapter. 

A cylindrical workpiece is ground in a manner 
similar to the finishing process used on a lathe 
(fig. 13-2). As the surface of the cylinder rotates 
under the grinding wheel (longitudinal traverse) 
the work moves from left to right (cross traverse). 

To select the proper work speed, take a cut 
with the work speed set at 50 feet per minute. If 
the wheel acts too soft, decrease the work speed. 
If the wheel acts too hard, increase the work 
speed. 

Wheel speed and work speed are closely 
related. Usually by adjusting one or both, you can 
obtain the most suitable combination for efficient 
grinding. 



GRINDING 



wo 


1ST. PASS 


v i y 


2ND. PASS 


U 


3RD PASS 




4RO PASS 


M- ~ mm 1 









> k 



CROSS 
TRAVERSE 



DEPTH OF CUT 

The depth of cut depends on such factors as 
the material of which the work is made, heat treat- 
ment, wheel and work speed, and condition of 
the machine. Roughing cuts should be as heavy 
as the machine can take; finishing cuts are usually 
0.0005 inch or less. For rough grinding, you might 
use a 0.003-inch depth of cut and then, after a 
trial cut, adjust the machine until you obtain the 
best cutting action. 

COOLANTS 

The cutting fluids used in grinding operations 
are the same fluids used in other machine tool 
operations. They are water, water and soluble oil, 
water solutions of soda compounds, mineral oils, 
paste compounds, and synthetic compounds. 
They also serve the same purposes as in other 
machine tool operations plus some additional 
purposes. As in most machining operations, the 
coolant helps to maintain a uniform temperature 
between the tool and the work, thus preventing 
extreme localized heating. In grinding work, 
excessive heat will damage the edges of cutters, 
cause warpage, or possibly cause inaccurate 
measurements. 

In other machine tool operations, the chips 
will fall aside and present no great problem; this 
is not true in grinding work. If no means is 
provided for removing grinding chips, they can 
become embedded in the face of the wheel. This 
embedding, or loading, will cause unsatisfactory 
grinding. and you will need to dress the wheel 



LATERAL 
TRAVERSE 




LONGITUDINAL TRAVERSE 



^ CROSS TRAVERSE ^ 



Figure 13-1. Surface grinding a flat workpiece. 



Figure 13-2. Surface grinding a cylindrical workpiece. 



cutting fluid are to reduce friction between the 
wheel and the work and to help produce a good 
finish. 

In most other machining operations, the 
primary property of a cutting fluid is its 
lubricating ability. In grinding, however, the 
primary property is the cooling ability, with the 
lubricating ability second in importance. For this 
reason, water is the best possible grinding coolant, 
but if used alone, it will rust the machine parts 
and the work. Generally, when you use water, you 
must add a rust inhibitor. The rust inhibitor has 
very little effect on the cooling properties of the 
water. 

A water and soluble oil mixture gives very 
satisfactory cooling results and also improves the 
lubricating properties of the cutting fluid. The 
addition of the soluble oil to water will alter the 
grinding effect to a certain extent. Soluble oil 
decreases the tendency of the machine and the 
work to rust, thereby eliminating the need for a 
rust inhibitor. When you prepare a mixture of 
soluble oil and water as a grinding coolant, use 
a ratio of three parts of water to one part of oil. 
This mixture will generally be satisfactory. 

The paste compounds are made of soaps of 
either soda or potash, mixed with a light mineral 
oil and water to form an emulsion. As a coolant, 
these solutions are satisfactory. However, they 
have a tendency to retain the grinding chips 
and abrasive particles, which may cause un- 
satisfactory finishes on the work. 

Mineral oils are used primarily for work where 
tolerances are extremely small or in such work as 
thread grinding, gear grinding, and crush form 
grinding. The mineral oils do not have as great 
a cooling capacity as water. However, the wheel 
face will not load as readily with mineral oils as 
with most of the other coolants. Therefore, using 
mineral oil allows you to select a finer grit wheel 
and requires fewer wheel dressings. 

When you select a cutting fluid for a grinding 
operation, consider the following characteristics: 

9 It should have a high cooling capacity to 
reduce cutting temperature. 



work 



It should prevent chips from sticking to the 



personnel. 

It should not cause rust or corrosion. 

It should have a low viscosity to permit 
gravity separation of impurities and chips as it is 
circulated in the cooling system. 

It should not oxidize or form gummy 
deposits which will clog the circulating system. 

It should be transparent, allowing a clear 
view of the work. 

It should be safe, particularly in regard to 
fire and accident hazards. 

It should not cause skin irritation. 

The principles discussed above are basic to 
precision grinding machines. You should keep 
these principles in mind as you study about the 
machines in the remainder of this chapter. 



SURFACE GRINDER 

Most of the features of the surface grinder 
shown in figure 13-3 are common to all planer 



IDOWN-FEED HANDWHEELl 




It should be suitable for a variety of 
machine operations on different materials, 
reducing the number of cutting fluids needed in 
the shop. 



28.249X 
Figure 13-3. Surface grinder (planer type). 



13-3 



*V r Wl*!. J.UVV }* XA.1XIVA. A. AS* ISfcbOJ. frf 

this machine are a base, a cross traverse table, a 
sliding worktable, and a wheelhead. Various 
controls and handwheels are used for controlling 
the movement of the machine during the grinding 
operation. 

The base is heavy casting which houses the 
wheelhead motor, the hydraulic power feed unit, 
and the coolant system. Ways on top of the base 
are for mounting the cross traverse table; vertical 
ways on the back of the base are for mounting 
the wheelhead unit. 

The hydraulic power unit includes a motor, 
a pump, and piping to provide hydraulic pressure 
to the power feed mechanisms on the cross 
traverse and sliding tables. The smooth, direct 
power provided by the hydraulic unit is very 
advantageous in grinding. The piping from this 
unit is usually connected to power cylinders under 
the traverse table. When the machine is operating 
automatically, control valves divert pressurized 
hydraulic fluid to the proper cylinder, causing the 
table to move in the desired direction. Suitable 
bypass and control valves in the hydraulic system 
let you stop the traverse table in any position and 
regulate the speed of movement of the table within 
limits. These valves provide a constant pressure 
in the hydraulic system, allowing you to stop the 
feed without securing the system. 

CROSS TRAVERSE TABLE 

The ways on which the cross traverse table are 
mounted are parallel to the spindle of the 
wheelhead unit. This allows the entire width of 
the workpiece to be traversed under the grinding 
wheel. 

Power feed is provided by a piston in a power 
cylinder fastened to the cross traverse table. 
Manual feed (by means of a handwheel attached 
to a feed screw) is also available. The amount of 
cross traverse feed per stroke of the reciprocating 
sliding table is determined by the thickness (width) 
of the grinding wheel. During roughing cuts, the 
work should traverse slightly less than the 
thickness of the wheel each time it passes under 
the wheel. For finish cuts, decrease the rate until 
you obtain the desired finish. When the power 
feed mechanism is engaged, the cross traverse 
table feeds only at each end of the stroke of the 
sliding table (discussed below); the grinding wheel 
clears the ends of the workpiece before crossfeed 
is made, thereby decreasing side thrust on the 
grinding wheel and preventing a poor surface 
finish on the ends of the workpiece. 



grinding machines in shipboard machine shops is 
usually 12 inches or less. It is not necessary to 
traverse the full limit for each job. To limit the 
cross traverse to the width of the work being 
ground, use the adjustable cross traverse stop dogs 
which actuate the power cross traverse control 
valves. 

SLIDING TABLE 

The sliding table is mounted on ways on the 
top of the cross traverse table. Recall that the 
sliding table moves from left to right, carrying the 
workpiece under the grinding wheel. 

The top of the sliding table has T-slots 
machined in it so work or workholding devices 
(such as magnetic chucks or vises) can be clamped 
onto the table. The sliding table may be traversed 
manually or by power. 

The power feed of the table is similar to that 
of the cross traverse table. During manual 
traverse, a pinion turned by a handwheel engages 
a rack attached to the bottom of the sliding table. 

During manual operation of the sliding table, 
table stop dogs limit the length of stroke. When 
power feed is used, table reverse dogs reverse the 
direction of movement of the table at each end 
of the stroke. The reverse dogs actuate the 
control valve to shift the hydraulic feed pressure 
from one end of the power cylinder to the other. 

The rate of speed of the sliding table, given 
in feet per minute (fpm), can usually be adjusted 
within a wide range to give the most suitable speed 
for grinding. 

WHEELHEAD 

The wheelhead carries the motor-driven 
grinding wheel spindle. You can adjust the 
wheelhead vertically to feed the grinding wheel 
into the work by turning a lead screw type of 
mechanism similar to that used on the cross 
traverse table. A graduated collar on the hand- 
wheel lets you keep track of the depth of cut. 

The wheelhead movement is not usually power 
fed because the depth of cut is quite small and 
any large movement is needed only in setting up 
the machine. The adjusting mechanism is quite 
sensitive; the depth of cut can be adjusted in 
amounts as small as 0.0001 inch. 

WORKHOLDING DEVICES 

Since surface grinding is usually done on flat 
workpieces, most surface grinders have magnetic 



13-4 



chucks. These chucks are simple to use; the work 
can be mounted directly on the chuck or on angle 
plates, parallels, or other devices mounted on the 
chuck. Nonmagnetic materials cannot be held in 
the magnetic chuck unless special setups are used. 
The universal vise is usually used when 
complex angles must be ground on a workpiece. 
The vise may be mounted directly on the 
worktable of the grinder or on the magnetic 
chuck. 

Magnetic Chucks 

The top of a magnetic chuck (see fig. 13-4) 
is a series of magnetic poles separated by non- 
magnetic materials. The magnetism of the chuck 
may be induced by permanent magnets or by 
electricity. In a permanent type magnetic chuck, 
the chuck control lever positions a series of small 
magnets inside the chuck to hold the work. In an 
electromagnetic chuck, electric current induces 



magnetism in the chuck; the control lever is an 
electric switch. For either chuck, work will not 
remain in place unless it contacts at least two poles 
of the chuck. 

Work held in a magnetic chuck may become 
magnetized during the grinding operation. This 
is not usually desirable and the work should be 
demagnetized. Most modern magnetic chucks are 
equipped with demagnetizers. 

A magnetic chuck will become worn and 
scratched after repeated use and will not produce 
the accurate results normally required of a 
grinder. You can remove small burrs by hand 
stoning with a fine grade oilstone. But you must 
regrind the chuck to remove deep scratches and 
low spots caused by wear. If you remove the 
chuck from the grinder, be sure to regrind the 
chuck table when you replace the chuck to ensure 
that the table is parallel with the grinder table. 
To grind the table, use a soft grade wheel with 
a grit size of about 46. Feed the chuck slowly with 




Figure 13-4. Magnetic chuck used for holding a tool grinding jig. 

13-5 



a depth of cut that does not exceed 0.002 inch. 
Use ample coolant to help reduce heat and flush 
away the grinding chips. 

Universal Vise 

The universal vise (fig. 13-5) can be used for 
setting up work, such as lathe tools, so the 
surface to be ground can be positioned at any 
angle. The swivels can be rotated through 360. 
The base swivel (A of fig. 13-5) can be rotated 
in a horizontal plane; the intermediate swivel (B 
of fig. 13-5) can be rotated in a vertical plane; the 
vise swivel (C of fig. 13-5) can be rotated in either 
a vertical or a horizontal plane depending on the 
position of the intermediate swivel. 

USING THE SURFACE GRINDER 

To grind a hardened steel spacer similar to the 
one mounted on the magnetic chuck in figure 
13-6, proceed as follows: 

1 . Place the workpiece on the magnetic chuck. 
Move the chuck lever to the position that energizes 
the magnetic field. 





28.251 

Figure 13-5. Universal vise (mounted on a tool and cutter 
grinder). (A) Base swivel; (B) Intermediate swivel; (C) 
Vise swivel. 



Figure 13-6. Grinding a spacer on a surface grinder. 



2. Select and mount an appropriate grinding 
wheel. This job requires a straight type wheel with 
a designation similar to A60F12V. 

3 . Set the table stop dogs so the sliding table 
will move the work clear of the wheel at each end 
of the stroke. If you will be using power traverse, 
set the table reverse dogs. 

4. Set the longitudinal traverse speed of the 
worktable. For rough grinding hardened steel, use 
a speed of about 25 fpm; for finishing, use 40 
fpm. 

5. Set the cross traverse mechanism so the 
table moves under the wheel a distance slightly 
less than the width of the wheel after each pass. 
(Refer to the manufacturer's technical manual for 
specific procedures for steps 4 and 5.) 

6. Start the spindle motor; let the machine run 
for a few minutes and then dress the wheel. 

7. Feed the moving wheel down until it just 
touches the work surface; then move the work 
clear of the wheel, using the manual cross traverse 
handwheel. Set the graduated feed collar on zero 
to keep track of how much you feed the wheel 
into the work. 

8. Feed the wheel down about 0.002 inch and 
engage the longitudinal power traverse. Using the 
cross traverse handwheel, bring the grinding wheel 
into contact with the edge of the workpiece. 

9. Engage the power cross traverse and let the 
wheel grind across the surface of the workpiece. 
Carefully note the cutting action to determine if 
you need to adjust the wheel speed or the work 

sneed . 



10. Stop the longitudinal and cross traverses 
and check the workpiece. 

Figure 13-5 shows a universal vise being used 
on a tool and cutter grinder in grinding a lathe 
tool bit. For this job, the base swivel (A) is set 
to the required side cutting edge angle, the 
intermediate swivel (B) is set to the side clearance 
angle, and the vise swivel (C) is set so the vise jaws 
are parallel to the table. A cup type wheel is then 
used to grind the side of the tool. The universal 
vise is reset to cut the end and top of the tool after 
the side is ground. 

The universal vise can be used on a surface 
grinder for very accurate grinding of lathe 
cutting tools such as threading tools. For example, 
to grind an Acme threading tool, set the vise 
swivel at 14 1/2 from parallel to the table. Set 
the intermediate swivel to the clearance angle. Set 
the base swivel so the tool blank (held in the vise 
jaws) is parallel to the spindle of the grinder. 
Remember to leave the tool blank extending far 
enough out of the end of the vise jaws to prevent 
the grinding wheel from hitting the vise. After 
grinding one side of the tool bit, turn it one-half 
turn in the vise and set the intermediate swivel to 
an equal but opposite angle to the angle set for 



the first side. This setting will result in a clearance 
equal to the clearance of the first side. 

Another method for grinding single point tools 
is to hold the tool in a special jig as illustrated 
in figure 13-4. The jig surfaces are cut at the angles 
necessary to hold the tool so the angles of the tool 
bit are formed properly. 

When you use either method for grinding tool 
bits, check the tool bit occasionally with an 
appropriate gauge until you have obtained the 
correct dimensions. To save time, rough grind the 
tool bit to approximate size on a bench grinder 
before you set the tool bit in the jig